342 'i*AYLOR : ON TEStACELLA SCUTULUM. 



veloped protuberance on the concave side of the tooth is much 

 nearer the posterior end. They seem also to be deficient of 

 the blade which I have detected on the convex side of the teeth 

 of haliotidea at the apical end. The figures of the dentition of 

 scutulum are carefully traced from a photograph taken by Mr. 

 Cooke of a Guernsey specimen and represent the 5 th and 13th 

 spinules of one of the middle series. Those of T. haliotidea also 

 represent the 5th and 13th teeth of one of the median rows, and 

 are copied from the photo, of a preparation by Mr. Butterell of 

 a Beverley specimen. 



There is however some variation, both in the aspect of the 

 teeth of the two species and also in their number — both of which 

 characters are said to be dependent on age — as Gray gives for 

 T. haliotidea, twenty longitudinal rows only, while Riramer 

 states fifty rows of fifty-one teeth each, for the same species. 



The STOMACH is whitish and spindle-shaped in T. haliotidea, 

 but oval and brown, with longitudinal whitish stripes in scutulum 

 and Jiiaugei, but no stress should be laid on these points, 

 as both the shape and color of this organ are a good deal de- 

 pendent upon the amount and condition of its contents. The glo- 

 bular enlargement of the canal, at the point where it receives 

 the biliaiy secretions is much more conspicuous in scutulum, 

 than in the other two species, and the liver in scutulum and 

 maugei is reticulated with white. 



Geographical Distribution. 



This species has been recorded under its varietal name from 

 France, Spain, England, Scotland and Ireland. The Irish records 

 are probably erroneous and may refer to T. haliotidea, as a spirit 

 specimen in my possession, collected at Youghal by Miss Ball, 

 is without doubt that species. So far as is definitely known at 

 the present time, T. scutulum is not found west of a line drawn 

 from the Isle of Wight to Cheshire. 



To help us to a better appreciation of what is known on the 

 subject, it will be advisable to give the distribution in detail 

 under each district in which it is stated to have been found. 



J.C, v., July, 188S, 



