22 JURASSIC FAUNA. 



No sutural line can be seen, but probably part of the body-ehamber is preserved. 



Locality and straiigraphical position. — Maz£ir Drik ; Polyphemus-Mmesione. 



Remarks. — This species is characterized by its evolute shell having very lovr 

 compressed whorls gradually increasing in heights a vride and tolerably deep um- 

 bilicus and strong ribs, which on the siphonal side are divided into two or three 

 finer branches, but almost entirely disappear in full-grown specimens. 



The specimens from Baluchistdn agree in this respect very well with the 

 original of fig. 1 of Professor Waagen's Perisphindtes aberrans, but they differ from 

 it by their lateral ribs being somewhat finer and apparently more numerous. On 

 the other hand, the ribs on the siphonal side are much better marked on the 

 Baluchistan specimens than on that of about the same size from Kutch. These are 

 unquestionably differences which must be noted, but I do not think them of 

 sufficient importance to justify the creation of a new species. Professor Waagen's 

 figures have been considerably restored, particularly fig. 16, and the ribs on the 

 posterior part of the last whorl crossing the siphonal side are wholly imaginary. 

 The original is badly damaged at this particular part, being so much worn away 

 on either side that only a middle piece of some 18 mm. in thickness remains, and 

 this does not exhibit the slightest trace of transverse ribs. In the original the 

 whoris are also much more compressed than is shown in the figure. 



