354 MOLLU^UA. 



iu tlic form of the respiratory organs, ami, like them, hve in tlie sea ; \n\i they are hermaphro- 

 dites, Uke the Niuhbranehiata and Puhuouea. 



ThB PLEeROBRANCHUS, CuV.''' 



The clouk and the foot l>oth jut beyond the l)oih', ^\hich tlius appeaia as if it were between two 

 biirklers. The formrr eontnins, in some sjieeies, a little ovul ealciireous phite ; in others, a horny one, 

 and in either ease it is situated above the head. Tlie brancliire are placed ahong the riglit side, in a 

 groove between the cloak and foot, and represent a series of pyramids divided into triangular leaflets. 

 Tlie mouth, in the form of a small proboscis, is overhung with an emarginate lip, and with two tuljular 

 cleft tcntacula ; the orifices of generation are before, and the anus behind the brancluJE. Tliere are four 

 stomachs, of which the second is fleshy, sometimes armed with osseous pieces, and the third is garnished 

 with prominent longitudinal laminae. The ijitesline is short. 



Tliere are different species in the Mcditerruiieiui and Imlian Ocean, some of which are lar^e and beautiful. f\Ve 

 ha\-e two British species.] 



The Pi.eurobilanchjEA, "Meckel [Plenrobranc/iiiJiuin, Blainv.), — 

 Has the branchia and tlie orifices of generation situated as in Pieurobranchus ; but the anus is above 

 the hranchiie ; the margins of the cloak and of the foot jiroject but a little, and upon the front of the 

 cloak are four short distant tentacula, forming a sfpiare which forces a eoinpanson with the anterior 

 disk of the Aceres. I find but one stomach, -with thin parietes, -which is a mere dilatation of the 

 intestine. A greatly divided glandular organ opens outwardly behind the genital orifices. There is no 

 trace of a shell. 

 The only knuwn species is from the Mediterranean. 



The Api.rsrA, Lin. 

 The margins of the foot arc turned np into flexiilc creisti, and, surrounding tlie hack on every side, 

 they can ite refiected over it. The head, supported on a neck uf greater or less length, has the two 

 siip''rior tcntacula hollowed like the ears of a quadruped, nnd two others of a flattened shape at the end 

 of the inferior lip ; the eyes at the base of the former. Upon the hack we find the branchiae in the 

 form of complicated leaflets, attached to a broad raembranous pedicle, and concealed hy a little cloak, 

 ei[ually membranous, which contains a horny fiat shell. The anus is behind the branchiae, and is often 

 concealed under the lateral crests : the vulva is to the right in front, and the penis issues from under 

 tlie right tentaculum. A groove, which extends from the vulva to the very extremity of the penis, 

 conducts the semen thither in copulation. A membranous crop, of en'?'"mous size, leads into a muscular 

 gizzanl, arnn?d inside with many cartilaginous ami pyramidal l>odies ; and this is I'ollnwed hy a third 

 stomach beset with sharp hooks, and a fourth iu the form of a Ciccum. The intestine is vulnminous. 

 These animals feed on sea-weed. A [leculiar gland jionrs out, through an orifice near the vulva, a 

 limpid humour, which is said to he very acrid in some S])ccies ; and from the edges of the cloak there 

 oozes in ahumlance a deep pm-ple liipiid, with wliM.'h ihc animal disetdonrs the water of tin- sea when it 

 perceives danger to he at hand. Their ova are laid in long glairy cntaujilcd tdaments, as slender as 

 threads. 



There are found in our seas Jj>!. fcvrid'n, Poirct, pmn/uft/, Ciiv., ■Audilrjii./au.'!, Linn. ; and the shurcsof forcii^n 

 coinitries possess several others. 



The Dolabeli.a, Lam. — 

 Dilfers only from Aplysia in the posiiion of the branchia^. at the posterior extremity of the boily, which 

 re^end>les a truncated cone. The lateral crest fits close to the branchial apparatus, leaving merely a 

 narrow groove. The shell is calcareous. 

 'J'liC species are found in the Mediterranean ami in the Indian (.)cean. 



Tnii NoTARCHUs, Cuv. — 

 Has the lateral crests united and covering the back, leaving merely a longitudinal fissure to conduct 

 water to the braneldrc. These have no cloak to cover them, but in other respects they resembJe the 

 branchiae of the Aplysia; and the organization of the tw^o gcnc-a is otherwise similar. Li 



• The ^.-imens Uu, L'n..rl/.,ri.i of Munlnf,m. [i, u.i:nc wliicli 11k B..t,iiiists liaic u-ur|icil,] iui.l lIil- B'frl/iclla ol BhiuiviKe. |_'l'''is g*;ilu3, V.ca- 



