MUSEUM OF COMPARATIVE ZOOLOGY. 295 



preserved valve are as follows: — Lon. of shell 45.0; of rostrum 16.0; max. alt. 

 of shell at right angles to the average plane of the hinge-line 26.0; alt. of ros- 

 trum at its middle part 4.0; double diameter of valve 18.0; of rostrum 8.0; 

 of rostral area 4.5 mm. For this variety (which may well prove with better 

 material to be a distinct species) I would propose the name microrhina. The 

 valves are extremely thick and internally radiately striate, the pallial sinus, 

 muscular scars, and buttress well marked, and fossette strong, ovoid and nearly 

 vertically directed. 



Cuspidaxia Jeffireysi Dall. 



Necera Jeffreysi Dall, Bull. M. C Z., IX. p. Ill, i881. 

 Plate m. Fig. 9. 



Habitat. Off Cape San Antonio, a fragment in 1002 fms.; Station 44, 539 

 fms. ; Yucatan Strait, 640 fms.; Station 136, in 508 fms., off Santa Cruz ; and 

 Station 230, off St. Vincent, in 464 fms., living, bottom temperature 41°.5 to 

 42°.0 F. 



This species is characterized especially, and distinguished from rostrata and 

 its other close allies, by the straightness of the hinge-margin and the conse- 

 quent elevation of the anterior dorsum, by the minute fossette, and by the 

 greatest ventral expansion being almost directly under the beaks. The pro- 

 portional length of the rostrum varies in different specimens, but it is less than 

 in obesa, and usually less than in rostrata. 



Cuspidaria obesa Lov^n. 



Necera obesa Loven (1846), Verrill, Trans. Conn. Acad., V. p. 563, pi. xllv. fig. 10 c, 



1882. 

 N. pellucida Stimpson, Inv. Grand Manan, 1853. 



Habitat. Barbados, 100 fms. 



A single specimen was found as above, and seems conspecific with the mori. 

 northern specimens dredged by the Fish Commission. I have also dredgec 

 this species in 16 fms., mud, near Catalina Island, off Santa Barbara County. 

 California : in companv with Plectodon scaler Cpr. and Cardiomya califomica 

 Dall. 



The valve figured (Plate III. fig. 1) is supposed to belong to this species, 

 though showing some points of difference on which more material is needed to 

 decide. 



