FISSUKEI.LID/E. 205 



Genus MACROCHISMA. 



Char. Gen. Molluscumgasteropodum; testapatellaeformi,oblo]iga, 

 dorsali, versus extremitatera posita ; testae foramine maximo, elon- 

 gate, prope marginem anticum posito, terminis elevatis. Obs. Mr. 

 Cuming remarks that the animal of this geuus is very large and 

 elongated, with the shell placed near the hinder extremity. The 

 shell has the compressed sides and elevated extremities of the 

 genus Fi-mirelliilea, but it is much prolonged backwards; and the 

 foramen is very long, narrowed behind, widened in front, where it 

 is placed close to the anterior margin of the shell, which is de- 

 pressed immediately in front of it. 



Species of Macrochisma. 



1. maxima (f. 216, 217), A. Adams. — Testa, oblonga, radiatim 

 striata, fusco et rubro radiatim fasciata, postice subdepressa, 

 obsolete bicostata ; margine antico valide elevato, sinuato, intiis 

 margine incrassato ; foramine antice angustato. Obs. This, and 

 not J/, hiatula, is the species figured in the 'Conch, lllust.' as 

 F. macrochisma. 



2. Sinensis (f. 219), A. Ad. — 21. maxima simili, sed tenuiore, 

 postice terminis valide elevatis. Obs. It is a thinner shell than 

 21. maxima, with the margin elevated at both extremities. 



3. axgustata (f. 225), A. Ail. — M. maxima, simili, sed angus- 

 tiore, ad latera oblique striata. Obs. Narrower than M. maxima, 

 with oblique striae at the sides. 



4. compressa (f. 218), A. Ad. — 21. maxima simili, sed lateri- 

 bus compressis, colore pallide fulvo, postice fusca, fascia rosea an- 

 tice utrinque radiata ; foramine valide attenuato. Obs. A much 

 narrower shell than 21. maxima, of a different colouring, and with 

 the fissure greatly lengthened. 



5. pkoducta (f. 224), A. Ad. — Elongata, alba, tenuissime ra- 

 diatim striata; antice margine vix elevato, postice margine de- 

 presso subrostrato ; costa postica elongata, depressa, striata, fora- 

 mine antice lato. Obs. Very long, depressed posteriorly by a 

 broad flat rib, and drawn out into a point or beak. 



6. megatrkma (f. 227), A. Ad. — Ovali, parva, tenui, alba, 

 postice roseo punctata, postice roseo biradiata, obtusa ; foramine 



vol. in. 2 B 



