MOLLUSC A. 785 



The heart lies in these molluscs in the middle of the body on the 

 dorsal surface, and receives the blood from the gills placed on each 

 side. MILNE EDWARDS unites this family with the preceding and 

 the next following into a common order under the name of Opis- 

 thobranchia. This family approaches, however, very near to the 

 preceding, and especially to the genera Doris and Tritonia. 



Phyllidia Cuv. Head with four tentacles, the two superior 

 retractile within a cavity. Anus in posterior and middle part of 

 back. 



Comp. CUVIEK Ann. du Mus. v. pp. 266276, PI. xvm. Mollusq., Mem. 



VIII. 



Sp. Phyllidia trilineata Cuv., PJiyll. varicosa LAM., Cuv. 1. c. figs, i 6, 

 BLAIKV. Malac. PI. 47, fig. i ; in the Indian and Red Seas, as also Phyl- 

 lidia pustulosa Cuv. ibid. fig. 8, LEUCKART in Atlas zu der Edze von 

 E. EUEPPELL, Wirbellose Thiere des rothen Meeres, p. 36, Tab. xi. fig. i. 



Pleurophyllidia MECK., Dtphyllidia Cuv., Armina E/AFIN. (on 

 the authority of CANTRAINE), Lingmlla BLAINV. Head with two 

 tentacles placed towards the back at the anterior margin of mantle. 

 Frontal veil with angle produced on each side. Vent in right side, 

 behind genital foramen. Mantle acuminate posteriorly. 



Sp. Pleurophyllidia lineata, Diphyll. lineata OTTO, Nov. Act. Acad. Cces. Nat. 

 Cur. xvii.; DELLE CHIAJE Memorie, i. p. 128, Tab. 10, figs. 12 20; 

 MECKEL Archiv f. d. Physiol. vin. 1823, Taf. n. figs, r /, s. 190 207, 

 CANTRAINE Malac. mediterr. p. 63, PI. 2, fig. 4, in the Mediter. and accord- 

 ing to LOVEN in the North Sea also. Diphyll. verrucosa CANTR. ibid. fig. 3. 

 Comp. Diphyll. ocellata DESK., R. Am., d. ill., Moll. PI. 31, fig. 2. (The 

 specimen from the collection of BRUGMANS, on which CUVIER founded tins 

 genus, now in the Rijks Museum of Leyden, Diphyll. Brugmans'd Cuv., is of 

 one colour, pale and with a smooth mantle.) 



Family VI. Pleurobranchiata. Marine gasteropods hermaphro- 

 dite, naked or furnished with a small internal shell, more rarely 

 external. Branchiae composed of divided laminse resembling leaves 

 pinnatind or supradecomposed, on one side only, where are also the 

 vent and orifices of generation, mostly situated on the right side or 

 backwards on the back, more or less covered by the mantle. 



This family, named by CUVIER Tectibranches, which was trans- 

 lated by many writers Pomatobranchia, by MENKE Crypsibranchia, 

 has no greater claim to this name, or even less than many other 

 divisions of molluscs. We adopt therefore the name of Pleurobran- 

 chiata instead of the sesquipedale of BLATNVILLE Monopleurobranchiata 



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