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Contributions in Science, Number 520 Squires: Pico Formation Paleontology & 83

Deme´re´, 1983); and Infierno Formation (Wilson, 1955), Baja regarded by modern workers as the author of this species. See
Californa Sur, Mexico. McLean (1978:19, fig. 7.2) for a description and illustration of it.
REMARKS. Argopecten invalidus is one of the most common The Pico Formation specimens differ by having a much smaller
megafossils in the study area, and its preservation is excellent. size, 10u wider pleural angle, lower spire, fewer and more widely
Specimens range from 3 mm to 67.6 mm in height. Although they spaced spiral ribs on last whorl, some beading, and fewer and less
can be weathered, they are unabraded, many have their fragile well-developed ribs on the base.
auricles intact, and many specimens are paired valves (i.e., According to McLean (1978:19), C. dolarium (Holten, 1802)
Table 1). is a synonym of C. canaliculatum. Moore (1968:56, pl. 27, fig. b)
illustrated a specimen that she identified as C. doliarium [sic]
Class Gastropoda Cuvier, 1797 from Pliocene strata in San Diego, and this particular specimen
Family Calliostomatidae Thiele, 1924 looks very similar to the Pico Formation gastropod in terms of
Genus Calliostoma Swainson, 1840 the spacing of the spiral ribs on the last whorl. The Pico
Formation gastropod differs by having fewer, more widely
TYPE SPECIES. Trochus conulus Linnaeus, 1758, designated spaced, and less well-developed ribs on the base, as well as by
by Herrmannsen, 1846; Holocene, Mediterranean Sea. having some beading on the spiral rib next to the suture on the
last whorl.
Calliostoma sp., aff. C. grantianum Berry, 1940
Figures 53–54 Family Muricidae Rafinesque, 1815
Genus Ocinebrina Jousseaume, 1880
REMARKS. This gastropod is represented by three specimens
from LACMIP loc. 17918. Preservation is very good, but two of TYPE SPECIES. Murex corallinus Scacchi, 1836, by original
the specimens are incomplete. The illustrated specimen, which designation; Holocene, North Atlantic and Mediterranean.
is the most complete one, consists of approximately 3.25
teleoconch whorls and is 5 mm in height. This gastropod is similar Ocinebrina sp., aff. O. fraseri (Oldroyd, 1920)
to Calliostoma grantianum Berry (1940:12–13, pl. 2, figs. 4, 5) Figures 77–79
from middle Pleistocene strata in San Pedro, Los Angeles County,
California. The Pico Formation specimens differ by having smaller REMARKS. This gastropod is represented by a single specimen
size, fewer whorls, wider pleural angle, more closely spaced spiral from LACMIP loc. 17918. Preservation is good, but the tip of its
ribs on the sides of the teleoconch whorls, beads on the spiral rib spire is missing, as well as some of the shell on the dorsal surface
adjacent to the suture on the last half turn of the last whorl, of the last whorl. The specimen, which is 19.3 mm in height, is
obsolete spiral ribs on the medial part of the flattish base, and three similar to the extant Ocinebrina fraseri (Oldroyd, 1920:135, pl.
rather than five ribs in the umbilical region. The immaturity of the 4, figs. 1–3), from the Pacific Northwest. Northeastern Pacific
Pico Formation specimens could explain the difference in size and species formerly placed in Ocenebra Gray, 1847 were transferred
fewer whorls. Mature C. grantianum have up to 6.5 whorls and to Ocinebrina by McLean (1996). The Pico Formation specimen
are 15.4 mm in height. There is a possibility that the Pico differs from Oldroyd’s species by having slightly stronger
Formation specimens represent a new species, but specimens that irregular varices, more and narrower spiral ribs, and reticulate
are more mature are needed for confirmation. sculpture on the spire whorls and posterior half of the last whorl.
The Pico Formation gastropod resembles C. canaliculatum The Pico Formation specimen is unusual for an Ocinebrina
(Lightfoot, 1786), whose chronologic range is late Pliocene to because it has both an immature-stage open siphonal canal and a
Holocene (Grant and Gale, 1931:833). This gastropod9s species mature-stage outer lip (i.e., outer lip interior with at least four
name stems from Martyn (1784:table 1, pl. 32), but his work was strong nodes). In Ocinebrina, the siphonal canal remains open
rejected for nomenclatural purposes by the International Com- until final maturity and the lip expands and forms labrial
mission on Zoological Nomenclature (1957:Opinion 456). As denticles (McLean, 1996:80). Future collecting might show that
noted by Rehder (1967:19), Lightfoot (1786:101, no. 2220) is this species is new.

r
left valve, height 23.2 mm, 31. 13. Limaria sp., cf. L. orcutii (Hertlein and Grant, 1972), hypotype LACMIP 14339, LACMIP loc. 17917, steinkern of
left? valve, height 45.7 mm, 30.5. 14. Myrakeena veatchii (Gabb, 1866), hypotype LACMIP 14340, LACMIP loc. 9659, left valve, height 68.8 mm,
30.5. 15. Myrakeena veatchii (Gabb, 1866), hypotype LACMIP 14341, LACMIP loc. 9659, right valve (juvenile), height 18.2 mm, 31.2. 16–19.
Argopecten invalidus (Hanna, 1924). 16. Hypotype LACMIP 14342, LACMIP loc. 9659, left valve (originally paired with following specimen), height
61 mm, 30.7. 17. Hypotype LACMIP 14343, LACMIP loc. 9659, right valve, height 60 mm, 30.7. 18–19. Hypotype LACMIP 14344, LACMIP loc.
9659, height 66.7 mm, 30.7. 18. left valve. 19. right valve. 20. Lyropecten catalinae (Arnold, 1906), LACMIP 14345, LACMIP loc. 7752, right valve,
height 122 mm, 30.4. 21. Swiftopecten parmeleei (Dall, 1898), hypotype LACMIP 14346, LACMIP loc. 17917, left? valve, height 53 mm, 30.6. 22.
Leopecten stearnsii (Dall, 1878), hypotype LACMIP 14347, LACMIP loc. 7752, right valve, height 57.2 mm, 30.6. 23. Patinopecten healeyi (Arnold,
1906), hypotype LACMIP 14348, LACMIP loc. 9659, right valve, height 58.6 mm, 30.7. 24. Pododesmus macroschisma (Deshayes, 1839), hypotype
LACMIP 14349, LACMIP loc. 17917, left valve, height 49 mm, 30.5. 25. Epilucina californica (Conrad, 1837), hypotype LACMIP 14350, LACMIP
loc. 7752, left valve, height 26.7 mm, 30.9. 26. Here excavata (Carpenter, 1857), hypotype LACMIP 14351, LACMIP loc. 17920, left valve, height
17.9 mm, 31.2. 27. Lucinisca nuttalli (Conrad, 1837), hypotype LACMIP 14352, LACMIP loc. 17918, right valve, height 14 mm, 31.7. 28. Lucinoma
annulatum (Reeve, 1850), hypotype LACMIP 14353, LACMIP loc. 17917, left valve, height 56.4 mm, 30.4. 29. Miltha xantusi (Dall, 1905), hypotype
LACMIP 14354, LACMIP loc. 17934, right valve, height 98.3 mm, 30.2. 30. Cyclocardia occidentalis Conrad, 1855, hypotype LACMIP 14355,
LACMIP loc. 7752, right valve, height 8.2 mm, 32.6. 31. Trachycardium (Dallocardia) quadragenarium (Conrad, 1837), hypotype LACMIP 14356,
LACMIP loc. 7752, left valve, height 73.3 mm, 30.4. 32. Chione (Anomalocardia) fernandoensis English, 1914, hypotype LACMIP 14357, LACMIP
loc. 17918, left valve, height 11.2 mm, 31.8. 33. Callithaca tenerrima (Carpenter, in Gould and Carpenter, 1857), hypotype LACMIP 14358, LACMIP
loc. 17918, right valve, height 85 mm, 30.2.