341 



Its umbilicus, which is rather deep and step-shaped, has a rounded 

 margin, and occupies about one-fourth of the whole diameter. On the 

 outer volution the surface markings consist of distant, narrow, low 

 and rather tlexuous, transverse ribs, which become fainter with age 

 and are almost obsolete near the aperture. On the periphery or siphonal 

 region, at a short distance from the aperture, si.K of the ribs are from nine 

 and a quarter to twelve and a quarter millimetres apart. The spaces 

 between these ribs are comparatively broad and nearly flat, and where the 

 test is preserved, the interspaces are marked with a few obscure minute 

 transverse riblets, or small, faint, rounded and very slightly raised ridges, 

 that are parallel to the ribs. 



In the Museum of the Survey there are four other specimens, which, 

 in the writer's judgment, possess essentially similar characters, and 

 therefore are probably also referable to P. Otacodensis. Three of these 

 are from the Comox River, near Comox, V.I., collected by Mr. Harvey 

 in 1893 : and one from Hornby Island, collected by Mr. Harvey in 1895. 



The figured specimen presented by Mr. Robbins, has been examined 

 b}^ Dr. Kossmat, who has for ^ arded the following notes in regard to 

 it. "No. 14 agrees in all essential characters with the types of P. 

 Otacodensis found near Otacod in the collection of Mr. Worth. Some- 

 times the umbilical wall of the Indian specimens is somewhat higher 

 than in No, 14, but this character is variable, and I have before me, also, 

 shells which agree in this feature with your specimen. The ribs of No. 

 14 fade off near to the umbilical wall, whilst in most of the Indian speci- 

 mens they reach down only to the middle parts of the sides ; but I have 

 seen in the Hector collection, a Canadian specimen, (mentioned in my 

 paper in the Jahrbuch K. K. Geol. Reichsanstalt) showing the same style 

 of sculpture as the Indian specimens, and there are, on the other hand, 

 individuals of otherwise typical P. Otacodensis, with relatively long ribsc 

 which also disappear near the umbilical wall, so that there is no specific 

 difierence betweeji the specimen from Vancouver and P. Otacodensis. 



" The only diflference, which seems to be constant, is the following : on 

 P. Otacodensis the ribs of the external region are relatively closely 

 arranged in young and old stages, whilst in a middle stage, (when about 

 6 or 7 cm. in diameter) the distance of the ribs apart is about 1 to 1^ 

 cm. (sometimes even more) while in the Canadian specimen the distance 

 is never so great. But I cannot think that this can be considered as of 

 specific value, though perhaps it might be desirable to regard the 

 Vancouver form as a local variety. The septa agree perfectly in the 

 arrangement of saddles and lobes, and in every detail. Plate LVi in 

 Stoliczka's work represents a specimen with relatively coarse ribs, but, as 



3— M. F. 



