MUSEUM OF COMPARATIVE ZOOLOGY. 439 



are attached on each side of the foot, and ramify from a central area of attach- 

 ment in a very large number of short stout spongy lobules, recalling the digita- 

 tions of some keratose sponges. The ova are minute and yellowish. The 

 hepatic granules are dark brown or grayish. The whole mass of the genito- 

 hepatic organs nearly fills the mantle cavity, and is larger than all the rest of 

 the soft parts put together. These lobules are not like the pyriform projections 

 of Myonera, each of which projects singly from the rounded surface of the 

 visceral mass, and probably subsides after the period of ovulation. In Grypto- 

 don the whole mass on each side arises from a single small area, and digitates 

 afterward. 



Several of the species referred to this genus in the Pelecypoda of the Chal- 

 lenger Expedition appear to me to belong near Lyonsia rather than with 

 Cryptodon, judging by the figures of the shell. 



In this connection I may observe that in a fine Lucina (of the type of 

 L. spinosa Eeeve), dredged in Panama Bay, I find the gill composed of a single 

 lamina, or sac, on each side, hanging vertically from the mantle ; the posterior 

 lower edges are connected under the anal region, shutting it off from the bran- 

 chial chamber; there are two small orifices without siphons, of which the anal 

 is considerably the larger, but the lobes of the mantle, except in the siphonal 

 region, are not connected below the adductors. As Lucina has been said to 

 have two gill laminse on each side, these facts are worth noting. 



Lucina lenticula, Reeve (I. p. 265). The specimens cited from Station 

 21, in 287 fins., and from Barbados, in 100 fms., prove on further study to be 

 young specimens of L. multilineata Conrad. 



Lucina sagrinata, Dall (I. p. 265). This species has since been dredged 

 off Cape San Antonio, in 300 fms., and at Station 2646, in 85 fms., off Cape 

 Florida, by the U. S. Fish Commission. 



Cardium ceramidum, Dall (I. p. 269). This species should be compared 

 with C. antillarum Orbigny. 



Meiocardia Agassizii, Dall (I. p. 271). This species is figured on 

 Plate XL. Fig. 7, and in Agassiz. Three Cruises of the Blake, II., p. 74, fig. 311, 



1888. 



Callocardia (Vesicomya) venusta, Dall (I. p. 274). This species is fig- 

 ured on Plate XL. Fig. 5, and in Agassiz, Three Cruises of the Blake, II. p. 75, 

 fig. 312, 1888. Isocardia cytherioides Mayer, Journ de Conchyl., XVI. p. 103, 

 pi. iii. fig. 6, from the Lower Helvetian beds of Northern Italy, belonging to 

 the Upper Tertiary, is probably a Vesicomya, judging by the figure. Another 

 fine species of Vesicomya was obtained on the voyage of the Albatross, off 

 Tobago, in 880 fms. , ooze. It is very nearly the form and color of Cythere* 

 albida, and reaches a length of an inch (25.0 mm.) or more. In this, which 

 will be described under the name of Vesicomya Smithii, in honor of Mr. E. A. 

 Smith of the British Museum, the teeth are closely like those of V. venusta, 

 but more developed, the shell being larger and stouter. The pallial line ia 



