MUSEUM OF COMPARATIVE ZOOLOGY. 5 



flattened and bounded by two obscure carina?, which is never present in 

 T. cubensis. The hinge teeth are slender and delicate, the deltidium much 

 narrower, and the foramen usually smaller than in T. cubensis. The shell 

 is widest behind the middle of the valves, giving a slight coffin-shaped 

 aspect to the valves ; the cardinal border is nearly straight, the cardinal 

 process is slender, produced, and square at the end. The cardinal plate is 

 divided, as in the last, the shelly plates on each side are nearly flat and 

 anteriorly emarginated. The crura are sharply pointed. The anterior 

 portion of the loop is but slightly convex in the middle, the gutters on 

 each side are broad and shallow, there are no lateral slits, and instead 

 of a median prolongation there is a deep, broad emargination or concavity 

 in the anterior edge of this part of this loop. Instead of a sinus behind, 

 there is a sharp point, which is, however, often broken off* in dry speci- 

 mens. The apex of the haemal valve is not incurved. In fact, the shell 

 of this species is flat where T. cubensis is concave, emarginated where 

 cubensis is produced, entire where cubensis is fissured, broadest where 

 cubensis is narrowest, narrowest where cubensis is widest, subcarinate 

 where cubensis is smoothly rounded, etc., etc. In both obscure fine radiat- 

 ing lines may be often seen. That these characters are constant through- 

 out hundreds of specimens of T. cubensis I can testify from actual exami- 

 nation. I have found those here recorded of T. vitrea constant in some 

 twenty specimens, and in all the figures of this species extant. Hence I 

 have not the slightest hesitation in considering them as distinct species. 

 The differences of the loops, solely, would distinguish them anywhere, and 

 no more satisfactory specific character could be advanced. 



In its general anatomy this species presents some similarity to Wahllu imia 

 Jiorblana. I shall r<"=erve a more explicit account of the structure for that 

 species, and only mention here the anatomical points which appear more 

 striking, and which are more or less peculiar to this species. Most of the. 

 soft parts are of a translucent yellowish white color. The mantle is of 

 stouter consistency than in W. fioridana, and may often be removed from 

 the shell with but little injury if care be exercised. The muscles are. 

 similar in disposition to those of the other members of the Terebratulidee, 

 and present no new features. The peduncle is solid, cup-shaped at its 

 extremity, and has the edge produced in cylindrical horny rootlets, which 

 are attached to foreign bodies. The regular arrangement in layers of the 

 muscles and corium, as well as the axial tube of the peduncle, found in 

 Lingula, is less evident or absent in these forms. In this species the 

 peduncle is very short and stout, broadly cordiform at its inner extremity 

 when enveloped by its various tunics. 



The brachia are arranged as in T. vitrea, as figured by Woodward; the 

 central coil makes about four turns. The cirrhi are very short behind the 



