190 PROCEEDESGS OF THE AC.U)EMT OF [April, 



line. Ribs 35, about as wide as the inten-als, granose in the left 

 valve, the graniilation obsolete in the posterior half of the right 

 valve. Teeth 13 and 34. an irregularity where the anterior and 

 posterior series meet. Edge fluted as usual. 



Length 19.5, alt. 17.5. diam. 16.5nim.:35ribs (tj-pe). 



Length 22.3, alt. 22, diam. of right valve 9.5 mm.: 33 ribs '^largest 

 valve; . 



Type No. 2964, A. X. .S. P. 



This species is much less obhque than -.4. tolepia, and approaches 

 more to a circular shape. It is known by 5 valves and one pair. 

 The valves are remarkably thick. 

 Area perfaceta d. sp. 



The shell is nearly equivalve. inequilateral with large, inflated 

 beaks at the anterior fourth: extremely globose. Lower-basal angle 

 a httle produced. Sculpture, in the left valve of 24 ribs about as 

 wide as their inter^'als, and ever^-where closely granose. Right 

 valve having the ribs much narrower than their inter^'als, smooth 

 in the median part, granose at the ends. Hinge rather short, with 

 13 teeth before, 25 behind an irregularity below the beaks. Margins 

 deeply fluted. 



Length 20.5. alt. 21.5, diam. of left valve 11.3 mm. 



T>-pe No. 2726, A. X. .-. P. 



A much smaller, more obese Argina than -4. tolepia. The nine 

 valves in the collection belonged to as many indi^'iduals. The 

 sculpture is particularly pleasing. 



Area pomponiana n sp 



The shell is rather thin, inflated, ver^' inequilateral, the beaks 

 inflated, cur^-ing strongly forward, between the anterior fifth and 

 sixth of the length. Cardinal area narrow and tapering behind the 

 beaks, verj- short and wider in front, marked with one or two angu- 

 lated grooves. Posterior end sloping, produced below. Sculpture 

 of the left valve, 28 ribs widei: than their inters'als, and even.-where 

 closely set with transverse granules. Right valve with the ribs 

 narrower, about equal to the inter\'als, flat-topped and rather low 

 and smooth except at the ends, where the}' are granose. Hinge 

 slender, with many fine teeth. 



Length 16. alt. 14.25, diam. of left valve 7.3 mm. 

 •• 19. ■• 15. " •• right •' 9 " 



Cotj-pes No. 2725. A. N. S. P. 



Thinner, more oblique than the preceding species, and differing in 

 details of sculpture. Five valves belong to as many indi\-iduals. 



