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UNITED STATES NATIONAL MUSEUM BULLETIN 296 



prominent teeth point forward along the ventral margin of the mantle. 

 Other teeth are very small and scattered about on the mantle. 



Figure 25. — Cryptophialus wainwrighti, new species, from Thais triseriallis from Soldado 

 Bay, Mexico: a, female, side view, with cyprid larvae; b, c, d, opercular horizons of differ- 

 ent specimens, rostral (attachment) end at right (i) and left (c, d); e, mandible;/, first 

 maxilla; g, larval or immature male; h, mature male; i, burrow aperture, surface view. 



There is no orificial knob, but the attachment disk is well developed, 

 and forms a horny disk of cemented exuviae bearing curious whole or 

 partial small disks scattered over its surface. 



The usual comb collar on the orificial velum guards the ventral 

 end of the interior of the aperture. 



The head is rounded and prominent, although not noticeably hairy. 

 A prominent labrum, which may be creased near the anterior end, 



