62 CLASS III. GASTEROPODA. ORDER VI. PULMOBRANCHIATA. 
Examples. 
P]. CLXI. Fig. 1 and 2. 
TESTACELLUS HALIoTOIDEUS, Draparnaud, Hist. Nat. des Moll. Terr. et 
Fluv., p. 121. pl. 8. f.43 and 48. and pl. 9. f.12 and 13. D’Orbigny, 
Moll. des [es Canaries, p. 49. 
Testacella Europea, De Roissy. 
Pl. CLXI, Fig. 3 to 6. 
TrstaceLLus Mavuegt, De Férussac, Moll. Terr., p. 94. pl. 8. f. 10 to 12. 
D’Orbigny, Moll. des Iles Canaries, p. 48. 
Testacella haliotoidea, Ledru. 
P]. CLXI. Fig. 7 to 10. 
TESTACELLUS scuTULUM, Sowerby, Genera of Shells, No. 1. 
VITRINA, Draparnaud. 
Testa externa, rotundato-ovata, subheliciformis, tenuis, fragilis, subde- 
pressa, epidermide viridi, nitente, induta, extremitatem posticam 
animalis supervolvens ; spira brevi; apertura amplissima, semilu- 
nari, latitudine superante ; margine simplici; columella lineari. 
The genus Vitrina, instituted by Draparnaud, is one of no little im- 
portance in the distribution of this class, inasmuch as it offers a striking 
transition between the very types of Lamarck’s grand divisions of Gaste- 
ropoda and Trachelipoda, namely, between the straight dilated form, as 
of Limax, and that which is spiral or turbinated, as of Helix. The Vi- 
trine somewhat resemble the Testacelli ; but instead of having a simple 
shell adhering to that part of the body which is the seat of the branchial 
