594 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.45. 



HALICARDISSA, ne^w genus. 



Shell recalling Halicardia and Verticordia, finely granuiose extern- 

 ally, with a few strong radial ribs; the distinctive characters are ana- 

 tomical. The shell has been figured.^ 



The soft parts recall those of Halicardia but instead of having a 

 thin netlike gill attached on each side to a more or less convoluted 

 fleshy siphonal septum, thus completing the separation of the pedal 

 and siphonal chambers, the septum is thin and incomplete behind, 

 so that it does not cut off the siphonal from the pedal chamber 

 completely, and the gills form no part of it but are free, except at 

 the proximal end, and appear to have both direct and reflexed 

 laminae; the foot is more like the usual pelecypod foot, with no devel- 

 oped opisthopodium, and the palps offer nothing exceptional. The 

 soft parts, in brief, are intermediate between those of Verticordia 

 proper and the ordinary pelecypod, anatomically, and much nearer 

 the former than to the typical Halicardia. 



Type. — Verticordia perplicata Dall, from 812 fathoms near the 

 Galapagos Islands. Cat. No. 266804, U.S.N.M. 



Shells of the genus Halicardia were referred to Mytilimeria by 

 Verrill and Locard, and the present species would from the shell 

 alone be suspected to belong to Halicardia. 



LYONSIA (ALLOGRAMMA) AMABILIS, new species. 



Shell thin, with a pale olivaceous periostracum and pearly interior, 

 the lithodesma small. The sculpture resembles closely that of the 

 type of the group, L. (A.) formosa Jeffreys, from the Canaries, but 

 differs in the following details; the anterior transverse ripples, the 

 central nodulous ray, and the radial ridge below the posterior dorsal 

 area are more vertically directed; on the latter area there is only 

 faint indication of the radial ribbing which in L. formosa is distmct 

 and minutely spinose; the anterior end is longer than the posterior, 

 while in formosa the reverse is the case; the coloration of the perio- 

 stracum is olivaceous green while in formosa it is ferruginous brown. 

 Length 23; of anterior end 12; height 15; diameter 12 mm. 



Santa Barbara Channel, California, in deep water. Cat. No. 

 267161, U.S.N.M 



This is a much larger shell than the Atlantic species of the same 

 group. 



LYONSIA (ALLOGRAMMA) OAHUSnSIS, new species. 



Shell resembling the preceding, but somewhat smaller, pale brown, 

 with the anterior transverse ripples fewer and less vertical than in 

 either of the other species, the median ray less distinct and wider, 

 composed of feeble undulations; the posterior dorsal area with low 

 transverse instead of radial sculpture over its lower half; the posterior 



' Proc. U. S. Nat. Mus., vol. 12, 1889, pi. 8, fig. 1, 



