CONCHIFERA. 319 



THETIS, Sowerby. 



Etym. Thetis, in Greek myth, a sea-nymph. 



Syn. Poromya (anatinoides) Forbes. Embla (Korenii) Loven ?. Inoce- 

 ramus (impressus) D'Orb. ? Corbula (gigantea) Sby. 



Type, T. minor, fig. 221. T. hyalina, PI. XXII. fig. 11. 



Shell sub-orbicular, ventricose, thin, translucent, surface regularly granu- 

 lated, interior slightly nacreous ; ligament (1) external ; hinge-teeth 1 or 2 ; 

 umbones strengthened inside by a posterior lamina; adductor (a, a') and pedal 

 impressions (p) separate, slightly impressed, posterior adductor bordered by a 

 ridge; pallial line nearly simple, sub-marginal. 



Animal with short siphons, the branchial largest, surrounded at their 

 base by 18 20 tentacles, generally reflected on the shell; mantle open in 

 front; foot long, narrow and slender. (M c Andrew.) 



Distr. 5 sp. Norway, Brit. Medit. Madeira, Borneo, China. 40 150 fms. 



Fossil, 7 sp. Neocomian . Brit. Belgium, France, S. India. 



Sub-genus ? Eucharis, Recluz ; Corbula quadrata, Hinds, Guadaloupe. 

 Shell equivalve, obliquely keeled, gaping ; beaks anterior ; hinge-teeth 1 1 ; 

 ligament external ; pallial line simple ; surface granulated. 



PANOP.EA, Menard de la Groye. 



Etyin. Panope, a Nereid. Ex. P. Americana, PI. XXII. fig. 12. 



Syn. ? Pachymya (gigas) Sby. U. Greensaud. Brit. France. 



Shell equivalve, thick, oblong, gaping at each end ; ligament external, on 

 prominent ridges ; 1 prominent tooth in each valve ; pallial sinus deep. 



Animal with very long, united siphons, invested with thick, wrinkled 

 epidermis ; pedal orifice small, foot short, thick and grooved below ; gills 

 long and narrow, extending far into the branchial siphon, the outer pair 

 much narrower, faintly pectinated ; palpi long, pointed and striated. 



In P. Norvegica the pallial line is broken up into a few scattered spots, 

 as in Saxicava ; the animal itself is like a gigantic Saxicava. (Hancock.) 

 This species ranges from Ochotsk to the White Sea, Norway and N. Britain ; 

 it was formerly an inhabitant of the Medit. where it now occurs fossil. 

 ( = P. Bivonte, Phil.) The British specimens have been caught, accidentally, 

 by the deep-water fishing-hooks. P. australis is found at Port Natal, buried 

 in the sand at low-water ; the projecting siphons first attracted attention 

 (doubtless by the strong jets of water they sent up when molested) but the 

 shells were only obtained by digging to the depth of several feet. The 

 Medit. sp. P. (jlycimeris attains a length of 6 or 8 inches. 



Distr. 6 sp. Northern Seas, Medit. Cape, Australia, New Zealand, Pata- 

 gonia. Low-water 90 fms. 



Fossil, 140 sp. Inf. Oolite . IT. States, Europe, India. 



