43 
Bacutites.—Shell straight, cylindrical, sometimes rather compressed, slightly conical; 
the partitions articulated by sinuous sutures: septa transverse, a little distant; the 
disk imperforated, lobed, and indented at the circumference. 
Plate XXII. Fig. 14. B. Faujasii. Fossil. [Mr. G. B. Sowerby’s Cabinet.] 
Driviston Il._- MONOTHALAMOUS CEPHALOPODA. 
Shell unilocular, wholly external, and enveloping the animal. 
ARGoNAUTA.—Shell univalve, unilocular, involute, very thin; spire bicarinated, tubercu- 
lar, turning into the aperture. 
Plate XX. Fig. 17. A. nitida. 
Drviston II. ~~» NAK ED CEPHALOPODA. —4 Genera. 
No shell either internal or external. A solid, free, cretaceous, or horny substance, is found in the 
_ inside of most of these animals. 
Ocropus.—No internal solid substance. 
Loticoprsis.—No internal solid substance. 
Lottco.—An elongated, thin, transparent, and horny lamina, inclosed in the interior of 
the body, near the back. 
Plate XX. Fig. 20. Lamina of L. vulgaris. 
Srrra.— free, cretaceous, spongy, and opake bone, inclosed in the interior of the bo- 
dy, towards the back. 
Plate XX. Fig. 18. S. officinalis. 
ORDER V. 
HETEROPODA. —3 Genera. 
Cartnarta.—Shell univalve, conical, flattened at the sides, unilocular, very thin, hyaline; 
the summit spirally turned, and the back sometimes furnished with an indented 
keel: aperture oblong, entire. 
Plate XX. Fig. 19. C. fragilis. [Icon.—Enc. Method. Pl. 464, fig. 3.] 
PTEROTRACHEA.—This genus has no shell. 
Puytirror.—This genus has no shell. 
G2 
