102 AMERICAN JOURNAL 



The genus Terehratula of Llhwyd, who was not a binomial 

 author, was adopted by Miiller (Prodr. Zool. Dan. 1776, pp. 

 xxxi and 249), although not in the restricted sense in which it 

 is at present employed. His Tcrehratulce embraced several spe- 

 cies now distributed in different genera. In 1799, Lamarck, in 

 his Prodr. Nouv. Class, des Coquilles, adopted the name, taking 

 T. perovalis, Sby., as his type. This example has been followed 

 by almost all subsequent authors. The generic term Anomia 

 used for species of this family by Bolten (1798), Linnaeus, and 

 other authors, has in modern times, with equal unanimity been 

 applied to a genus of Lamellibranchiate mollusca. 



The type most commonly cited for the genus is the recent 

 Terebratula vitrea of Born (= Anomia terehratula, Lin. Syst. 

 Nat. 1153, and Gryphus vitrea, Megerle, Berl. Mag. 1811, p. 

 64), which inhabits the Mediterranean and is found fossil in the 

 Pliocene deposits of Sicily. 



Terebratula unguicula, Cpr. 



T. unguicula, Cpr., Proc. Zool. Soc. Feb. 14, 1865, figs. 1 to 

 4, p. 201. Cooper, Geogr. Cat. of Cal. Mollusca, p. 3, 

 No. 3. 



Hab. San Diego, 6 fm. ; Monterey, 20 fm.. Cooper. Van- 

 couver Id., Forbes. Sitka, under stones at low water ; Unga 

 Id., 4 fms., Dall. 



This remarkable and very distinct species is provided in the 

 young state with strong, radiating, simple ribs, and in this con- 

 dition the haemal valve resembles, exteriorly, a small Pecten. In 

 older specimens the ribs bifurcate and become less pronounced, 

 and the resemblance to a young Terehratulina caput-serpentis 

 becomes more marked. The principal differences are that the 

 Terehratula is rather the wider, and the intercostal spaces are 

 more channelled than in the Terehratulina. Even these differ- 

 ences may not be constant in a large number of specimens. The 

 broad incomplete loop, of course, is abundantly sufficient to 

 identify this species. The umbo of the neural valves is sharply 

 pointed in perfect specimens ; the foramen is large and incom- 

 plete, the area smooth and very short ; there is no deltidiura, 

 and the pedicel is usually stout and short. 



Smithsonian Cabmet, 14,789, 14,892, 15,264. 



No. 16,232, a single valve from Neeah Bay, appears to be 

 Terehratella caurina, Gould, jun., worn. 



