OF MOLI/USCA. 153 



setose ; the lateral vibracula are 3 • 3, setose, half-retractile ; bran- 

 chial plume minute ; operculum multispiral. 



The mantle of Gibbula lineata is even, but the pillar-lappet often 

 forms a branchial fold ; head-lappets two, small, suboval, lateral ; 

 the neck-lappets are only a continuation of the operculigerous lobes, 

 the one on the pillar side breaking into eight or ten dentations, the 

 outer one plain Clark, Moll. 309. 



14. Margarita. 



Shell subglobose, thin, polished or striated ; axis umbilicated, 

 open ; aperture nearly circular ; pillar-lip ending in a point ; throat 

 iridescent. Operculum of many rather gradually enlarging whorls. 



1. M. helicina, Adams, Gen. Moll. t. 49. f. 60, operculum; Forbes 

 $■ Hartley, B. M. t. C.C. f. 4. 



Lingual membrane of Margarita antarctica linear, transparent, 

 rather dilated in front. Teeth 00 • 5 * 1 • 5 • 00 ; central tooth elon- 



Fig. 83. — Teeth of Margarita antarctica. 



gate, dilated in front ; upper edge concave, very transparent ; inner 

 lateral 3*3 or 5 ■ 5, linear, bristle-like, arched, acute, rather far 

 apart ; middle lateral strong, transparent, with a strong transparent 

 apical hook ; outer lateral very numerous, crowded, slender, hooked 

 at the end (fig. 83). 



The skin of Margarita is reticulated. Tentacles hispid, with very 

 minute tubercles, channeled above, with a minute internal lobe. Eye- 

 pedicel free, short, united by a frontal veil. Foot with a large ante- 

 rior lobe and lateral beards, grooved above behind. — Loven. 



Prehensile collar of Margarita helicina distinct. Teeth 00"6" 1 - fi - 00; 

 the central thirteen subsimilar, strap-shaped ; apex recurved, denticu- 

 lated, the middle one rather the broadest ; lateral numerous, subu- 

 late, recurved at the tip. — Alder. 



•\-\ Pillar-lip slightly twisted in front. 



15. Tegula. 



Shell elongate, top-shaped; axis imperforate, covered with a 

 callous deposit ; pillar spirally twisted, ending in a large prominent 

 tubercle in front. 

 1 . T. pellis-serpentis. 



The axis of this shell is rarely perforated. 



