22 MOLLUSCA. CEPHALOPODA. 



S. Peronii, Lam. Shell white, fragile, about an inch in diameter. 

 ' Seldom occurs perfect. Inhabits American seas. Klein, Ost. 

 pi. 1, %. 6. 



FAMILY VII. ORTHOCERATA. 

 Shell straight, or nearly so ; not spiral. 



Gen. 28. CONILITES. 



Shell conical, straight, slightly inflected, having a thin outer 

 crust distinct from the nucleus which it contains ; nucleus 

 somewhat separable, multilocular, divided by transverse sep- 

 ta. (Fossil.) 



Gen. 29. HIPPURITES, Lam. 



Shell cylindraceo-conical, straight, or a little arcuate, multilo- 

 cular, with transverse septa; an internal lateral channel, 

 formed by two parallel, longitudinal, obtuse, and convergent 

 ridges, the last cell closed by an operculum. (Fossil.) 



Gen. 30. NODOSAKIA, Lam. 



Shell elongated, straight, or slightly arcuate, subconical, nodose, 

 with bulgings at the place of the cells ; transverse septa per- 

 forated. 



N. radicula. Shell straight, oblong, attenuated ; the articulations 

 globular, smooth; the syphon sublateral. About 2 lines long. 

 Inhabits the Adriatic Plancus, pi. 1, fig. 5. 



Gen. 31. ORTHOCERA, Lam. 



Shell elongated, straight, or a little arcuate, subconical, mark- 

 ed externally with numerous longitudinal grooves; cells 

 formed by transverse septa, perforated by a tube, which is 

 either central or marginal. 



O. raphanus. Shell straight, elongated, conical, articulate, the ar- 

 ticulations bulging ; the syphon sublateral. Inhabits the Medi- 

 terranean Plancus, pi. 1, fig. 6. 

 The shells of this genus are very minute. Many recent species have been found on 



the British coasts ; and fossil species occur in this country in clay- slate of the coal 



formation, carboniferous limestone, and lias. See Fleming's British Animals, 



p. 235, &c. 



Gen. 32. BELEMNITES, Lam. 



Shell straight, elongated, conical, separable into two parts ; the 

 outer a solid sheath, full above, excavated with a conical cell 

 beneath; the inner a conical multilocular nucleus, divided 

 by numerous transverse septa, perforated by a central tube. 

 (Fossil.) 



The British fossil species of this genus are found in the lower oolite, lias, and 

 chalk marl. 4 



