94 ZOOLOGY. 



Tribe Decacera, 



Fam. 2. Sqmda\ Sejna (j)l. TG, fc/. 77) has the body siuTOunded by a 

 narrow fin ; and of the ten arms, two are pednncnlated and longer than the 

 rest. A light friable oblong-oval and spongy shell, usnally named "cuttle- 

 bone," is contained within the back. The contents of the ink-bag in this 

 animal are dried and nsed by painters under the name of sejna. 



Fam. 3. Lolhjidm. Lolujo (Z. loligo., Linn., fl. "IQ^Jig. 76) has the body 

 slender, with lateral fins, the shell thin, horny, and translucent; twd 

 pedunculated arms longer than the rest, and the eyes are without a lid, bnl 

 covered with a transparent membrane. Its motion backM'ards throngli the 

 water by means of its funnel, is extremely rapid, and it sometimes throM's 

 itself out of the water, or upon land. The species are much used for food, 

 especiall}' in China. 



Fam. 4. Lol'igop8id(X. Loligojms has a slow motion, the shell is 

 corneous, the body slender and translucent, and has few muscles. 



Fam. 5. Teuthidldce. Onyclioteiitli'is (already referred to) has a corneous 

 internal shell, a slender body, with a triangular fin upon each side posteriorly, 

 uniting upon the back. 



Fam. G. BelemnitidcB. Shell corneous, conical, largest anteriorly, and 

 containing a series of chambers, posteriorly pierced by a siphuncle, and 

 inserted in a hard case or helernnon.^ which is generally pointed posteriorly. 

 The family is extinct, but its remains are abundant in a fossil state in the 

 oolitic and cretaceous formations. 



Fam. 7. Spirxdido2. The genus Sjpirida {S. sj)irula,pl. 76, Jig. 13) is the only 

 one in the family, and until recently it contained but a single described species. 

 The shell is a thin open spiral (not twisted longitudinally as represented in the 

 figure), with numerous partitions concave externally, through which a small 

 ventral siphuncle runs. The shell is internal, at the posterior extremity of the 

 body. There are ten arms, of which two are larger than the rest. The 

 common species inhabits the Atlantic and Pacific Oceans, and although the 

 shell is common, the animal is very rare, and requires further examination. 



The second order, Tentaeidrfera, contains two lamilies : JVautilidce, and 

 Ammo7vlfddw. 



Fam. 1. JV^autilidm. In the geinm JV^ciidUus {If.2:>07njpilius, Linn., 2^^- 76, 

 Jig. 16), the shell is spiral, many-chambered, the partitions transverse, 

 concave externally, their margins simple ; a central siphuncle passing 

 through them ; the whirls in contact, the last enveloping the preceding ones. 

 Kautilus pompilius is the best known species; the shell is nacreous, orna- 

 mented with irregular reddish bands, the umbilicus closed. It is six or 

 eight inches in diameter, and inhabits the Indian and Pacific Oceans. A 

 second species is known, iV^. umMlicatus, which is raucli rarer than the 

 former, and has the centre of each side widely umbilicate, so that the 

 whirls can be counted. The history of the order is taken from If. 

 pompilixis. The animal is contained in the last open chamber of the shell ; 

 it has a pediform appendage for creeping, and when it walks upon the 

 bottom, the aperture is downwards. The jaws are like a reversed parrot 

 298 



