246 BULLETIN OF THE 



A. With smooth margin. 



Nucula segeensis (Forbes) Jeffreys. 



Nucula tenuis Montagu, Dall, Bull. M. C. Z., IX. p. 123. 

 Niicula (Bgeensis Jeffreys, P. Z. S., 1879, p. 681. 



Habitat. Sigsbee, off Havana, 175 and 450 fnis. ; off Morro Light, 292 

 fms.; Station 20, 220 fms.; Station 3, 450 fnis.; and Station 230, near St. 

 Vincent, in 464 fms. ; all mostly dead valves. 



In examining specimens dredged oflf the Carolinas by the Fish Comnussion, 

 I was struck by the fact that only N. proximo, and not a single N. tenuis had 

 been secured. This led me to review the specimens identified for me by Dr. 

 Jeflfreys as N. tenuis, and so named in the preliminary report, as above. I 

 have compared them with all the varieties of tenuis, and with all the specimens 

 of (Bgeensis in the Jeffreys collection. The Blake specimens, nearly all being 

 separated valves, agree in form and general appearance with the flatter forms 

 of tenuis, the only external differences -being that the former are a little more 

 pointed and pinched dorsally behind, and that two moderately distinct ridges 

 enclose a very narrow elongated area along the upper posterior margin. 

 Symptoms of such an area were visible occasionally in individuals of genuine 

 tenuis, but not so clearly defined. Inside, the hinge line of tenuis is narrower, 

 the teeth more delicate and perhaps fewer, the cartilage pit a little smaller. 

 These are just the differences which separate tenuis from N. cegeensis, and it is 

 probable that the Blake specimens should be referred to the latter species. It 

 is by no means clear to me that cegeensis is anything more than a geographical 

 race of tenuis; but so far, though the hinge characters are slight, I have not 

 found many intermediate specimens. The West Indian specimens are larger 

 than those from the Mediterranean, and consequently the number of teeth is 

 greater, but the proportion is about the same in all. The largest specimen 

 measures 10.7 max. Ion., 8.0 max. alt., and 4.7 mm. max, diam., with 8 anterior 

 and 15 posterior teeth. 



Nucula C3miella, n. s. 



Shell small, white, rather thick, rounded, triangular, moderately convex; 

 beaks somewhat anterior, not prominent; exterior sculptured with evenly 

 distributed concentric waves or narrow lirae separated by wider interspaces; 

 an obscure flexuosity in front of the beaks indicates, without sharply defin- 

 ing, a lunule over which the concentric sculpture passes; a faint ridge ex- 

 tends backward from the beaks half as far as the teeth, but becomes obsolete 

 without enclosing an area ; inside, the shell is brightly pearly, the margin 

 plain, with seven anterior and eight or nine posterior rather stout teeth, sepa- 

 rated by a good-sized cartilage pit, directed vertically downward from the 



