DE. T. DAVIDSON ON RECENT BRACHIOPODA. 25 



correspond to the inner sinuses, pass off from their internal margins, and divide once 

 or twice " (/. c. p. 840). 



Terebratulina caput-serpentis, var. unguiculata. (Plate V. figs. 38-40.) 



Terebratula unguicula, V. Carpenter, Proc. Zool. Soc. 1865, p. 201, figs. 1-4; Cooper, Gcogr. Cat. 

 California. Moll. p. 3, 1866 ; Dall, Amer. Journ. of Conch, vol. vi. p. 102, 1870, and Report on Brachiop. 

 of Alaska, 1877; S. T. Whitcaves, On Some Marine luvertebrata from the West Coast of North 

 America, Canadian Naturalist, n.s. vol. viii. p. 464, 1878. 



Shell ovate, longer than wide ; valves almo.st equally convex, rounded laterally and 

 in front ; lateral sides of the umho strongly auricular, especially in young and middle- 

 aged specimens. Ventral valve evenly convex, but sometimes very slightly depressed 

 anteriorly ; beak short, obliquely truncated by a rather large incomplete foramen, margined 

 anteriorly by the umbo of the dorsal valve and by two small lateral deltidia. Surface 

 of valves marked with numerous radiating delicate riblets, simple aud stronger at their 

 origin, but rapidly augmenting in number from bifurcation and by the interpolation 

 of shorter riblets between the longer ones. Valves crossed with concentric raised striaj. 

 Loop short and simple, the crura disunited in the young, annelliform in the more advanced 

 age. Colour light yellowish white. Length 13, breadth 10, depth 5 lines. 



Hab. San Diego, Cal., to the Aleutian Islands, San Pedro, Cal. (Cooper) ; Neeah Bay 

 (W. T. Swan) ; Victoria (V. W. Lord, J. Richardson) ; Port Etches ; Sliumargin Islands ; 

 Unalaska (Dall). Eange : low Avater to 100 fathoms, those from deep water, the largest, 

 adhering to shells and stones (Dall). At Race Island lighthouse, and Victoria Harbour, 

 in 30 to 70 fathoms; end of Texada Island, in 40 to 70 fathoms, mud (Richardson). 



Obs. Mr. Dall states, in the paper already referred to, that this species is readily 

 separated from Terebratulina caput-serpentis, T. japonica, and other species, which 

 strongly resemble it externally, by the broad loop, which is usually open, instead of being 

 closed, as the genus requires. However, it finally becomes closed in fully adu.lt specimens, 

 which reach the size of T. caput-serpentis. I have also had the advantage of being able 

 to examine a large number of young and adult examples of Carpenter's species, which 

 were kindly lent to me by Mr. Whiteaves, as well as others which I purchased from 

 Mr. G. B. Sowerbv, who had obtained them direct from Vancouver Island. After havinsr 

 minutely compared their exterior and interior with a large number of European speci- 

 mens of T. caput-serpentis, I arrived at the conclusion that T. unguicula is no more 

 than a variety of Linne's species. Carpenter's specimens, as he himself admits, were all 

 of small size, and consequently the crura of the loop were disunited. The specimens of 

 T. unguicula I was able to open had not the broad loop described by Dall, but agreed 

 well with the European specimens of T. caput-serpentis which I had previously opened 

 and examined. In these specimens of T. unguicula, the front line was rounded, and 

 not indented; but this is also the case with very many examples of T. caput-serpentis. 



In a letter dated December 1884, Mr. Dall writes me that he would not wish to be 

 quoted as believing T. unguicula distinct from T. caput-serpentis *, aud would be only 



* [Dr. Davidson has given three excellent figures (sec PL V. figs. 35, 30, <fe 37) of the well-marked variety of 

 Terehratulina caput-serpentis from the Mediterranean Sea, to which Dr. Gwj-n Jeffreys gave the varietal designation 

 of mcditcrranea. He described it as longer aud more slender than T. caput-serpentis, " more compressed or flatter than 



SECOND SERIES. — ZOOLOGY, VOL. IV. 4 



