698 DEEP WATER MOLLUSKS AND BBACHIOPODS—DALL. vouxvn. 



U. S. Fish Commission in 1885. The shell measured 45 mm. wide and 

 higli by 39 raai. loug. No. 50785, U.S.N.M. 



The shell is wide and angular, resembling a large Remicardium, with 

 a granular ashy-white or pale brown granulose surface, showing faint 

 traces of radiating ridges. The hinge is obsolete, an obscure swelling 

 represents the sublunular tooth in the right valve and a still feebler 

 one in the left valve. In Euciroa the left portion of the lunule is the 

 most prominent; in Halicardia the opposite is the case. The litho- 

 desma is an asymmetrical slender, solid, shelly arch, with the right limb 

 decidedly longer than the left one. The inner margin of the shell is 

 smooth, the valves are a very trifle unequal and shut closely. 



To facilitate comparison the characters of the soft parts are given 

 in the same prder as under Euciroa. 



The mantle, in its thickness and consistency, resembles that of 

 Euciroa. Its margin is thick and solid, and the inner ridge more dis- 

 tinctly papillose than in Euciroa, but not conspicuously so. The lobes 

 of the mantle are first separated in front of the middle of the anterior 

 adductor and continue so, backward, about halfway to the siphon, 

 thus leaving a shorter pedal opening than in Euciroa. The thickened 

 mantle-edge frames the perisiiihonal area, and its two sides are united 

 above and a little in front of the posterior adductor. In the lobes of 

 the mantle behind the siphon there is nothing corresponding to the 

 muscular areas of Euciroa. Th6 siphons recall those of Poromya. The 

 excurrent siphon is small, short, surrounded by insignificant granular 

 papillaj irregularly distributed sparsely over the perisiphonal surface; 

 a single larger but still very small papilla is visible in the median line 

 above the siphon, and distant half the diameter of the orifice. The 

 edges of the siphon are thin and entire; between it and the incurrent 

 siphon the surface of the perisiphonal area is finely granular and some- 

 what impressed. The branchial siphon is enormous, its longest diam- 

 eter externally about one-sixth the total circumference of the mantle.' 

 It is surrounded by a single row of long, strong tentacular processes, 

 flattened on their inner faces, rounded and inflated outwardly, and 

 covered with a distinctly granular epithelium. There are fourteen on 

 each side, and one in the median line above, not differing from the rest. 

 Externally these tentacles (as contracted in alcohol) areas long as one- 

 fifth the greatest diameter of the whole siphon, and are of nearly equal 

 size and length. They are surrounded by a cingulum rising from the 

 perisiphonal area elevated and constricted; from within, the wall of 

 the siphon is seen to be formed by parallel cylindical prominences 

 which continue the tentacula forward to the base of the siphonal tube. 

 The siphonal valve is circular, broad, and with a thin edge finely 

 crenulated. The valve occupies the base of the siphon like a perfo- 

 rated diaphragm, and does not project inward. Above it the siphonal 

 sej)tum is narrow, smooth, and a little produced forward in the median 

 Hue. There is no special set of muscular libers inserted upon the viilve 



