ball] new species of shells 163 



MOHNIA CLARKI Dall, n. sp. 



Shell small, plump, white, with a light green periostracum, usually 

 much eroded, with about five whorls ; apex defective in all the speci- 

 mens ; early whorls with (about eleven) small, arcuate, axial riblets, 

 extending from suture to suture, obsolete or absent on the last whorl, 

 their interspaces wider, shallow ; no spiral sculpture ; whorls flattish, 

 suture distinct, not appressed ; aperture white, body and pillar not 

 callous ; pillar twisted, nearly pervious ; canal narrow, recurved ; 

 outer lip arcuate, thin, simple ; operculum paucispiral. Lon. of shell 

 (decollate), 21 ; of last whorl, 16.5; of aperture, 12 mm. Max. lat. 

 of shell, 10.5 mm. 



U. S. Nat. Mus., 110,497; at station 4797, in 682 fathoms, Okhotsk 

 Sea, and 110,498, at station 4815, in 70 fathoms, off Hakodate, 

 Japan. 



A very simple, pretty little species which would seem when per- 

 fect to have rather a blunt apex, which is, however, eroded in every 

 specimen. Named in honor of Mr. Austin H. Clark of the "Alba- 

 tross" party. 



Genus YOLUTOPSIUS Morch 



VOLUTOPSIUS MIDDENDORFFII Dall, var. EMPHATICUS, nov. 



Shell resembling V. middcndorifii in form, size, and coloration, but 

 heavier, thicker, with the spiral sculpture more emphatic, and broken 

 irregularly by conspicuous incremental lines, so that its course forms 

 a series of minute zigzags. These differences, which seem unim- 

 portant when analyzed, affect the general aspect of the shell to a dis- 

 proportionate extent, so that at a first glance it seems very different. 

 The differences between the type from the eastern part of Bering 

 Sea and these from the west seem to hold good with all the speci- 

 mens. Lon. of shell, 90 ; max. lat., 48 mm. 



Station 4813, July 18, 1906, in 200 fathoms, Sea of Japan; 4804, 

 June 24, in 229 fathoms Okhotsk Sea, and 4982, September 19, in 

 390 fathoms, Sea of Japan. U. S. Nat. Mus., 110,486 (types), 

 110,485, and 110,487. 



VOLUTOPSIUS? KENNICOTTI Dall, var. INCISUS, nov. 



Shell resembling V. kennicotti in nearly all features, but distin- 

 guished by the much deeper and sharper minute spiral grooving, 

 which gives to the interspaces the aspect of minute crowded spiral 

 threads ; the axial ribs ( about fifteen in number) are also notably 

 prominent and strong. Lon. of shell, 75 ; max. lat., 35 mm. 



Station 4779, in 54 fathoms, Bering Sea, June 9, 1906. U. S. Nat. 

 Mus., 110,488. 



