166 AMERICAN JOURNAL 



group. It is to be hoped that in his forthcoming 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 some three hundred 

 specimens of Terebratula cubensis, Pourtales, and a critical com- 

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

 forced to the conclusion that the two species are distinct, though 

 closely allied; while among the specimens dredged by the Coast 

 Survey Expedition I found some which seemed to be unmistak- 

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



T. vitrea. 



Lateral margins horizontally 



rectilinear. 

 Hcemal valve rounded ovate. 

 Looj) with its sinuosity indented 



before, with a sharp point 



behind. 

 Hinge teeth close together, 



slender. 

 Deltidium narrow, small. 

 Shell somewhat compressed. 



T. nihensis. 

 Lateral margins flexuous. 



Hcemal valve quadrangulate. 



Looi? 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- 

 bensis and T, uva, 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. 



Reference to Plates. — Plate 6. 

 Fig. 1. Terebratella caurina^ Gld., normal; nat. size. 

 2. \ II « u varieties ; " 



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



5. " Obolella'' polita, Hall. Interior of neural valve, some- 



what reduced from Hall's figure. 



6. Same ; interior of haemal valve. 



