352 



MOLLUSCA. 



branous laminn? to cover fhem in time of dant^cr: and besides tlie two conoid tentacula in front, siuiilar to Ib^^se 

 of Doris, they liave fonr, or sometimes six otliers, which are simply pointed. 

 The Tritonies {Tri/oniay Cuv.), — 

 Have a bodv, superior teutctcula, and generative organs, as in tlie Doris ; liut the anus and tlie vent of 

 the peculiar secretion arc on tlte right side, behind the vulva : 

 tlie arbuscular branchix are aiTanged along each side of the 

 back, and the mouth, guarded Ijy Ijroad membranous lips, is 

 armed \\ithiu ^vitll t%YO lateral horny and cutting jaws, in sha})C 

 somewhat like to the scissors for shearing sheep. 



We have a large species {Tritonia Hombergii, Cuv.) on our coasts ; and 

 there are many others, some of them very small, which exhibit o^reat variety in the size and figure of their branch ice. 

 [il/e^/ico', Rang, differs in having filiform simple tentacula issuing from a wide sheath, and two series of ovate 

 muricated or tuberculated branchiae on the back, which readily fall off when the animal is handled. M. rofiea, 

 which bves on floating sea-weeds near the Cape of Good Hope, is the type ; but there are some European Mollusca, 

 of small size, which are also refiiruble to it,] 



The Theth'^'s, Linn., — 



^f^^T^%^lV^ 



Have along tbe back two rows of tufted 

 branchia: ; and upon the head a very large 

 membranous fringed veil, wliicli curves, in its 

 contraction, under the mouth. The mouth is 

 a membranous proboscis T\'ithout jaws: there 

 is at the base of the veil two compressed 

 tentacula, from the margin of wbich issues a 

 small conical point. Tlie orifices of generation, 

 of the intestine, and of the pecnUar secretion, 

 are as in Tritonia. The stomach is mem- 

 branous, and the intestine very short. 



There is, in the Mediterranean, a beautiful spe- 

 cies of a greyish colour, spotted \\ith \s\i\\.t {TheCts 

 fimbria, Linn.). 



The Scvll-ea, Linn. 

 Fi,;. iw.-Th.thysicporina, ^pper«r,r) unrLrpirie.. j^ tlus gcnus tlic body is conijiressed ; the 



foot narrow and furrowed, to enable it to embrace the stems <if sea- 

 weed ; no veil ; the mouth forming a smaU proboscis ; the exterior 



orifices as in Thethys ; the tentacula compressed, terminating in a 



cavity from which a htlle point, with an unequal surface, can be 



protruded; and upon the back are two pairs of membranous crests, 



carrying, on tlieir inner aspect, some pencils of branched filaments. 



The middle of the stomach is covered with a fleshy ring, armed 



with horny lauiinre as sliarp as a kiiiJV. Tlie comniou species is found on Fucus naians, or gulf-weed, 



wherever tlils appears. 



The Glaucus, Forstcr, 



Have the elongate body and the vents as in the preceding ; four minute conical tentacula ; and on each 



side [two or] three branchia?, each formed of hing fringes ar- 

 ranged like a fan, and by whose means tliey swim. They are 

 little cliarming Molluscs of the Mediterranean and Indian 

 C)cean, agreealjly painted with azm'e-lilue and silver, and swim 

 with great quickness on their Ijacks. Their anatomy cluscly 

 resembles that of Tritonia. The species have not. as yet, been 

 satisfactorily distinguislicd. 



The Laniogerns, Blainv., has, on each side, two series of little 

 plates, finelydivided in a pectinate manner, which are thebranchiie. 

 The body is shorter and tliicker than in Glaucus, but they have its 

 four little tentacula. 



The Eolidia, Cuv., 

 Resemble little slugs, with four tentacula above, and two on 



r.g l&S.— GhucuB For? 



