MAZATLAN UNIVALVES 307 



stoma. 1491, 1 sp. on fragment of Spondylus, with Bryozoa, 

 &c. 1492, 1 sp. on Uvanilla unguis. 1493, 2 separate sp., of 

 which one has deep sculpture. 



355 b. PBlVONIA PCONTORTA, VOT. INDENTATA. 



It. t. "B. contorts" simili, sed minore ; colore hand rosed; 

 sculpturd indentatd ; costis paucioribus ; interstitiis profundis, 

 cancellatis. 



This form would hardly be distinguished as a species from 

 the shell alone, so variable is the sculpture of Vermetidse, 

 even on the same specimen ; but as it is not improbable that 

 the second Bivonoid operculum, which is quite distinct, be- 

 longs to it, it is here kept provisionally separate. It is of 

 smaller growth, and yet of much coarser sculpture ; with a 

 different shade of colour, which in this family appears to be of 

 some importance. Long. *5, diam. apert. '05. 

 Hob. Mazatlan ; very rare, on Spondyli &c ; L'pool Col. 



Tablet 1494 contains 3 specimens. 



356 PBlVONIA ALBIDA, 71. S. 



IB. t. parvd, albidd ; anfr. ii. primis lavibus, turbinoideis, 

 subelevatis, posted amplectatis ; anfr. normalibus subregulariter 

 spiraliter contortis, marginibus subparallelis, ad sese plerumque, 

 ad concham alienam parum, adhcerentibus ; rugis concentrids 

 plus minusve expresses, spiralibus nullis. 



Both sculpture, colour and size mark this species as distinct, 

 although only 2 extremely young specimens and one with 

 about 5 normal whirls were found. This measures long. *22, 

 lat. *1, diam. apert. '03. 



Hab. Mazatlan : extremely rare, off Spondylus ; IS pool Col. 

 Tablet 1495 contains a young and the adult specimen. 



357. PBlVONIA , sp. ind. (a.) 



Tablet 1496 contains 2 minute Spirorbiform specimens, and a 

 portion of a separate non-spiral tube, only '02 in 'diameter, 

 which do not appear to be the young of any of the former 

 species. They are of a pale colour, and are nearly smooth. 



