MAZATLAN UNIVALVES 307 
stoma.—1491, 1 sp. on fragment of Spondylus, with Bryozoa, 
&¢e.—1492, 1 sp. on Uvanilla unguis.—1493, 2 separate sp., of 
which one has deep sculpture, 
355 6. PBIVoNIA PCONTORTA, var. INDENTATA. 
B.t. “B. contorte” simili, sed minore ; colore haud roseé ; 
sculpturd indentata ; costis paucioribus ; tnterstitiis profundis, 
cancellatis. 
This form would hardly be distinguished as a species from 
the shell alone, so variable is the sculpture of Vermetide, 
~ 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. 
Hab.—Mazatlan ; very rare, on Spohdyli &e; L’pool Col. 
Tablet 1494 contains 3 specimens. 
306 P BIVONIA ALBIDA, 2. s. 
B. t. parva, albida ; anfr. i. primis levibus, turbinoiders, 
subelevatis, postea amplectatis ; anfr. normalibus subregulariter 
spirahiter contortis, marginibus subparallelis, ad sese plerumque, 
ad concham alienam parum, adherentibus ; rugis concentricis 
plus minusve expressis, 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 ; ZL’pool Col. 
Tablet 1495 contains a young and the adult specimen. * 
357. P Brvonta ————, 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. 
