VO i8^ n '] PROCEEDINGS OF THE NATIONAL MUSEUM. 277 



arates this range of processes from the margin of the branchial orifice, 

 which is profusely papillose with arborescent papillae. A Innate de- 

 pression lies between this and the much smaller, plain-edged, nearly 

 linear anal orifice, while in front of it the pedal opening forms a minute 

 narrow slit, with granulated margin. In this form the palps are repre- 

 sented by a slightly raised edge around the mouth, not produced or 

 elongated at the sides. A languette or curtain valve hangs behind the 

 branchial orifice below the narrow septum. 



The balance of characters will perhaps carry Mytilimeria and Lyon- 

 siella to the Anatinidcc, or a family by themselves, rather than to the 

 Yerticordiidw, where I first placed them. But they are transitional in 

 their relations, and in spite of the relations between the form of the 

 gills in Lyonsiella and Lyonsia, I am still inclined to think the former 

 almost equally close to Verticordia, A supposed discrepancy, noted by 

 Pelseneer, arises from the fact that, instead of comparing Lyonsiella 

 with a genuine Verticordia, like acuticostata, as I did, he compares it 

 with a species of Poromya, which is, of course, a very different thing. 



Family VERTICORDIIDiE. 

 Genus VERTICORDIA Wood. 

 Verticordia (Wood) Dall, Mns. Comp. Zool. Bull., vol. xii, p. 285, 1886. 

 Verticordia acuticostata Philippi. 



V. acuticostata Dall, op. cit., pp. 285, 288. 



Hab. — Cuba, Barbados, and Gulf of Mexico, Blcike expedition; Mecl- 

 iterraneauj Philippi; North Atlantic, Jeffreys; Japan, A. Adams. U. 

 S. Fish Commission Stations 2659, off Cape Canaveral, in 509 fathoms, 

 bottom temperature 15°.2; and 2750, off St. Bartholomew, West Indies, 

 in 496 fathoms, sand, temperature 4.1°.4. 



This species grows to a considerable size, the two Fish Commission 

 stations affording valves 19 and 20.5 nn " in height respectively. 



Soft parts. — Another specimen, and are-examination of the one re- 

 ported on in 1886, confirm the description then given. There are no 

 palpi, the anterior pair are wholly unrepresented, the posterior or lower 

 pair may be represented by two small rounded hardly elevated tuber- 

 cles between the mouth and the anterior ends of the gills. The foot is 

 relatively extremely large, round, and stopper-like. The gills in the 

 second specimen are clearly aduate, asiuPelseneer's figure of Lyonsiella, 

 papyracea Smith (Chall.Eep. Anat, Moll., PI. in. Fig. 1), except that they 

 are underlaid by the solid fleshy siphonal septum, and do not serve 

 to supplement that septum as they are alleged to do in Lyonsiella abys- 

 sicola. They are proportionately very much smaller, hardly reaching 

 behind the middle of the foot. I suspect that the free end of the gill 

 in my first specimen was separated by a lesion, and is not normal, but 

 that the gill is always aduate in the adult condition. 



