534 



Hamites obstrictus, Jimbo. 



Plate 44, fig. 3. 



Hamites cylindraceuH ? Defrance. Whiteaves. 1879. This volume, pt. 2, p. 113, pi. 

 XIV, figs. 2 and 2 a ; but not H. cylindraceus of Defrance or 

 d'Orbigny. 

 Hamites obstrictus, Jimbo. 1894. Beitr. zur Kenni. der Fauna der Kreidefonn. von 

 Hokkaido, in Dames and Kayser's Palteontol. Abhandl., N. Ser., 

 vol. VI, p. 38, pi. 7 (23), figs. 2 and 2 a-h. 

 Hamites obstrictus, Whiteaves. 1896. Trans. Royal Society of Canada for 1895, Second 

 Series, vol. i, sect. 4, p. 130. 



" Posterior extremity of the shell unknown, the prolonged and 

 reflected portions slender, straight, almost circular in outline in trans- 

 verse section, unless when abnormally compressed, and separated from 

 each other by a space about equal in width to the maximum diameter of 

 the reflected portion, near the aperture. 



" Surface marked by prominent, narrow, simple and rarely bifurcating 

 transverse ribs, which are rounded at their summits and separated by 

 rather deep concave furrows. Besides the ribs, or rather furrows, there 

 is a single transverse constriction on the reflected portion of the shell. 

 On the prolonged portion the ribs are about one millimetre apart, but 

 on the reflected portion they are nearl}^ two millimetres apart. 



" Sutural line as represented on Plate 14, fig. 2 o, of the second part 

 of " this volume. 



" Sucia Islands, J. Richardson, 1874 : one crushed specimen, with the 

 sutural line well preserved. North-west side of Hornby Island W. 

 Harvey, 1893: two good specimens, one of them apparently free from 

 distortion. All three, upon the whole, agree remarkably well with 

 Jimbo's description and figures of H. obstrictus, although in that species 

 there are two transverse constrictions of the prolonged portion of the 

 shell, as well as one on the reflected portion, and the lobes and saddles of 

 its sutural line are perhaps not quite so numerously incised as those of 

 the specimen from the Sucia Islands." (Whiteaves, 1896, op. cit. supra, 

 pp. 130 and 131.) 



Quite recently the Imperial University of Tokio, per Mr. H. Yabe, has 

 presented to the Museum of the Survey an authentic Japanese specimen 

 of JI. obstrictus. This specimen, though only a cast of the interior of 

 the shell, with no portions of any of the sutural lines preserved, seems to 

 be essentially similar to and practically indistinguishable from, the speci- 

 men collected at the Sucia Islands by Mr. Richardson. 



