240 Scientific Proceedings, Royal Dublin Society. 



serrated along the median three-fifths of edge with minute denticles, and 

 with the smooth portion somewhat expanded at each end. Nine to thirteen 

 rows of teeth, diminishing considerably in size, are present in a radula ; the 

 median tooth would appear to be very flexible, an end being sometimes 

 curved up completely and entangled among the lateral teeth, which latter 

 are frequently broken. In size the median tooth far exceeds that of any 

 other known member of the family, which as yet seems to be limited to the 

 species of Boas and Meisenheimer, mentioned in the present paper, and 

 Thalassopterus zancleus, Kwietniewski (1910, p. 271). The hook-sacs of the 

 specimen, measuring 3 mm. in total length, measure 1'50 mm. in length by 

 1 mm. in breadth ; each contains about fifty gold-glittering hooks, all 

 reaching to the mouth of the sac; their roots form an oblong honeycomb 

 pattern along inner side ; the hooks nearest the mouth of sac are about 

 one-third the length of those at the furthest extremity ; all are widest at 

 base and taper to curved points. The genital duct shows the bladder-like 

 widening, as in T. diaphanus. The shape of penis with its pouch also agrees 

 in general detail with that species. 



