166 



AMERICAN JOURNAL, 



group. It is to be hoped that in his forthcojiing memoir upon 

 the subject he will give us Ms definition of a mollusk and of a 

 worm, in order that we may more clearly comprehend the mo- 

 tives which have led him to unite two-thirds of the 3IoUuscoidea 

 with the Annelids. 



I would add that, after an examination of s^ime three hundred 

 specimens of Terebratida cuhensis, Pourtales, 'and a critical com- 

 parison of them with a large series of T. vitred,, that I have been 

 forced to the conclusion that the two species ai;e distinct, though 

 closely allied; while among the specimens dre^lged by the Coast 

 Survey Expedition I found some which seemec? to be unmistak- 

 ably T. vitrea. The characters appeared to be- about as follows: 



T. e-uhensis. 

 Lateral margins flexuous. 



Hcemal valve quadrangulate. 



Loop indented behind, with a 

 rather broad, squarish pro- 

 longation in front. 



Hinge teeth more widely sepa- 

 rated, stout and thick. 



Deltidium wider, longer. 



Shell inflated. Foramen gen- 

 erally larger in proportion. 



I have been thus explicit, as several excellent foreign natural- 

 ists have expressed the opinion that the species are identical. I 

 have not had an opportunity of making a comparison of T. cu- 

 hensis and T. nva, Brod. 



The remarks in this paper upon the species described by Dr. 

 A. A. Gould may possess some additional significance from the 

 fact that they are made from an examination of his original type 

 specimens. 



T. vitrea. 



Lateral margins horizontally 



rectilinear. 

 Hcemal valve rounded ovate. 

 Loop with its sinuosity indented 



before, with a sharp point 



behind. 

 Hinge teeth close together, 



slender. 

 Deltidium narrow, small. 

 Shell somewhat compressed. 



Fig. 



Reference to Plates. — Plate 6. 

 1. Terehratella caurina, Gld., normal; nat. size. 

 ^- I " " " varieties ; " " 



4. " suffusa, Rve. ; loop. nat. size. 



5. " Obolella" p)olita, Hall. Interior of neural valve, some- 

 what reduced from Hall's figure. 



6. Same ; interior of haemal valve. 



