GASTKROPODA HETEROPODA. 51 



The Argonauta vitrea of authors, Favanne, vii, c, 2; Martini, I, 

 xiii, 163, must be tlie shell of a large Carinaria, but the animal is not 

 yet known. 



Atlanta, Lesueur*. 



The Atlantee of Lesueur, according to the recent observations of M. 

 Rang, are animals of this order, the shell of which, instead of being- 

 well opened like that of a Carinaria, has a narrow cavity, spirally 

 convoluted on one plane ; its contour is relieved by a thin crest. 



They are extremely small MoUusca from the Indian Ocean, 

 in one of which Lamanon thought he had discovered the original 

 Cornu Ammonisf — Atlanta Peronii and Atlanta Keraudrenii, 

 Lesueur, Journ. de Phys., Ixxxv, Novemb. 1817; and Rang, 

 Mem. de la Soc. d'Hist. Nat., tome 111, p. 373, and pi. ix. 



FiROLA, Peron. 

 The body, tail, foot, branchiae and visceral mass as in the Carinaria, 

 but no shell has ever been observed; the snout is elongated into a re- 

 curved proboscis, and the eyes are not preceded by tentacula. From 

 the end of the tail is frequently observed to proceed a long articu- 

 lated iillet, which Forskahl took for a Tsenia, and whose nature is not 

 yet very clearly ascertained. 



One species, the Peterotrachea coronata, Forsk. ; Peron., 



Ann. du Mus., XV, ii, 8, is very common in the Mediterranean, 



and M. Lesueur describes several from the same sea, which he 



considers as diiferent. — Journ. Acad. Nat. Sc. Philad., Vol. I, 



p. 3, but which require further comparison^. 



M. Lesueur distinguislies the Firoloidce, where the body, instead 



of terminating in a compressed tail, is abruptly truncated behind the 



visceral bundle, lb. p. 37§. 



To these two, now Avell known genera, I presume we must add, 

 when better understood, the 



TiMORiENNA, Quoy and Gaym. 

 Voy. de Freycin., Zool. pi. Ixxxvii, f. 1, which appears to be a Firola 

 divested of its foot and bundle of viscera ; and the 



MOXOPHORA, Id.\\ 

 Voy. de Freycin., Zool. pi. Ixxxvii, f. 4, .5, which has nearly the form 

 of a Carinaria, but is without a foot, distinct bundle of viscera, and 

 shell. 



* We must not confound the Atlantte of Lesueur with the Atlas described by him in 

 the same place, and which, so confused is his description, I do not know how to 

 class. 



t Voyage de Lapeyrouse, IV, p. 134, and pi. 63, f. 1 — 4. 



J Firola mutica; — F. gibbosa; — F. Forskalea; — F. Cuviem, which is the Pfero- 

 Irachea coronata, Forsk. ; — F. Fredcrica, copied Malacol. Blainv., pi. xlvii, f. 4 ; — 

 F. Peronii. — Add, Plervtrachea rufa, Quoy and Gaym., Voy. de Freycin., Zool. 

 pi. 87, f. 2 and 3. 



§ Firolo'ida Demarestia ; — Fir. BlainviUiana ; — Fir. aculeata, Less. 



II We must not confound them with the Monophorse of M. Bory Saint-Vincent, 

 (Voy. aux Isles d'Afr.,) which are Pyrosomse. 



e2 



