144 MANUAL OP THE MOLLUSCA. 



Shell pyi-amidal, with nearly a flat base ; wliirls numerous, flat, variously 

 striated ; apertiu'c oblique, rhombic, pearly inside ; columella 

 twisted, slightly truncated ; outer lip thin ; operculmn horny, 

 multi-spiral. Fig. 88 (T. pica). 



Animal with 2 small or obsolete head-lobes between the 

 tentacles ; neck lappets large : sides ornamented with lobes, 

 and 3 — 5 cirri ; gill very long, linear ; lingual teeth 11, den- 

 ticulated ; uncini — 90, diminishing outwards. 



Bistr., 150 sp. World-wide. Low- water to 15 fathoms ; the smaller 

 species range nearly to 100 fathoms. 



Fossil, 360 sp. Devonian — . Europe, N. America, Chile. 



Sub-genera. Pyraniis, Chemn., Tr. obeliscus, PL X., fig. 6, columella 

 contorted, forming a slight canal. 



Gibhula, Leach. Tr. magus, Brit. Shell depressed, widely umbilicated ; 

 whirls tumid. Head-lobes largely developed ; lateral cirri 3. 



Margarita, Leach. Tr. helicinus. PI. X., fig. 7. SheU thin ; cirri 5 on 

 each side. Distr., 17 sp. Greenland, Brit., Falkland Islands. Near low- 

 water, imder stones and sea- weed. 



Elenchus, Hmnph. (= Cauthiridus, Montf.) E, iris. PI. X., fig. 8. 

 Smooth, thin, imperforate, with a prominent base. Australia, N. Zealand. 

 T. iris scarcely differs in form from Ti'. zizyphinus ; E. badius is like a 

 pearly phasianella ; and E. varians (bankivia, Menke) would be called a 

 chemnitzia, if fossilized. PI. X., fig. 9. 



RoTELLA, Lamarck. 



Etym., diminutive of rota, a wheel. (Syn., Helicina, Gray !) 

 Type, R. vestiaria. PI. X., fig. 10. 



Shell, lenticular, polished ; spire depressed ; base callous ; lingual teeth 

 13 ; uncini numerous, svib-equal. 



Distr., 10 sp. India, Philippines, China, New Zealand. 



MoNODONTA, Lam. 



Etym., monos, one, and odous, (odontos) a tooth, 



Syn., labio, Oken. Clanculus, Montf. Otavia, Risso. 



Types, M. labeo. PI. X., fig. 11. M. pharaonis. PI. X., fig. 12. 



Shell, tm-binated, few- whirled ; whirls spirally grooved and granulated ; 

 lip thickened internally, and grooved ; columella toothed, more or less pro- 

 minently and irregularly; operc. horny, many- whirled. 



Distr., 10 sp ? W. Africa, Red Sea, India, Australia. 



Fossil, (included mth trochus) Devonian — . Eifel. 



Delphinula (Roissy), Lam. 

 Etym., diminutive oi ddphimis, a dolphin. (= Cyclostoma, Gray !) 



