r0 1889. n '] PROCEEDINGS OF THE NATIONAL MUSEUM. 267 



Dating fan-like in several .scallops or subsidiary Hat denticles. The 

 groups related to this genus are as follows: 



PALLIAL LINE SIMPLE. 



Kelliella (miliaria) Sara. Teeth well figured by G. O. Sars. Size small ; teeth small, 

 short, angular, ligament largely internal. 



Vesicomya (atlantica) Dall. Size variable to large, teeth Iamelliform, long, very flat, 

 the middle one hardly curved, hardly separable from the thin long posterior la- 

 mella, deeply severed from the anterior and largest lamella ; ligament wholly ex- 

 ternal. 



Callocardia s. s. (C. guttata) Adams. Cardiual teeth arched in the left valve, short ; 

 ligament in a deep groove, chiefly external ; posterior lamella separate, thin, 

 rather long. 



PALLIAL LINE DEEPLY SINUATED. 



Callogonia (Leeana) Dall. Anterior cardinal and middle lamella continuous, angu- 

 larly bent like a flattened M! ; posterior lamella short, high, separate; ligament 

 inset but wholly external. Right valve with middle tooth strong deeply angu- 

 lated, posterior lamella absent or represented by a spur or point just below and 

 behind the posterior limb of the middle tooth ; above this a socket for the re- 

 ception of the posterior lamella of the other valve. The anterior lamella thin, 

 concave upward, its edge somewhat irregular, sometimes faintly notched. 



It is almost impossible by words to describe comprehensively these 

 curious lamellar teeth ; the reader may, however, with the- aid of the 

 figures, understand fairly well how they are arranged. The teeth of 

 Kelliella are less lamellar than those of the other groups, are shorter 

 and more triangular. The genuine fry of Isocardia cor, with which 

 Jeffreys confounded Kelliella miliaris, has much thinner, flatter, more 

 parallel teeth, very like those of Vesicomya, plus a lateral tooth. 



The group named by me Veneriglossa in 188G (Atopodonta of Cossman, 

 1887) may belong here, and in that case would follow Callogonia, hav- 

 ing a moderately sinuated pallial line. 



The species known to belong to the groups above mentioned are as 

 follows : 



I. Kelliella miliaris Philippi (-\-abyssicola Sars). 



II. Vesicomya subquadrata Jeffreys sp.; V. atlantica, V. pacifica, and 

 V. Adamsi Smith; V. pilula and V. venusta Dall. 



III. Callocardia guttata A. Adams, C. allnda and C. Smithii Dall. 

 The last was, before it was thoroughly studied, referred by me to Vesi- 

 comya. 



IV. Callogonia Leeana Dall. 



Subgenus CALLOCARDIA s. S. 

 Callocardia guttata A. Adams. 

 Plate x, Fig. 5. 

 Callocardia guttata A. Adams, Ann. Mag. Nat. Hist, xin, p. 307, 1864. 



The figure above referred to is reproduced for comparison from the 

 drawing of the unique left valve iu the British Museum, for which I am 



