HAMITE. 277 



should have become extinct, simultaneously with the last 

 of the Ammonites, at the termination of the Chalk forma- 

 tion. 



Hamite. 



If we imagine a Baculite to be bent round near its centre, 

 until the smaller extremity became nearly parallel to its 

 larger end, it would present the most simple form of that 

 cognate genus of chambered shells, which, from their fre- 

 quently assuming this hooked form, have been called Ha- 

 mites. At PI. 44, Fig. 9, 11, represent portions of Hamites 

 which have this most simple curvature; other species of 

 this genus have a more tortuous form, and are either close- 

 ly coiled up, like the small extremity of a Spirula, (PI. 

 44, Fig. 2,) or disposed in a more open spiral. (PL 44, 

 Fig. 8.*) 



It is probable that some of these Hamites were partly 

 internal, and partly external shells ; where the spines are 

 present, the portion so armed was probably external. Nine 

 species of Hamites occur in the single formation of Gault 

 or Speeton clay immediately below the chalk, near Scar- 



• Both these forms of Hamite bear the same relation to Ammonites that 

 Lituites bear to Nautili; each being nearly such as shells of these genera 

 would respectively present, if partially unrolled. See Pliillips' Geol. York- 

 shire, PI. 1, Figs. 22, 29, 30. 



Baculites and Hamites have two characters which connect them with Am- 

 monites; first, the position of the Siplumcle, on the back, or outer margin 

 of the shell, (PI. 14, Figs. 5'', c. 8% a. 10, 11, a. 12, a. 13, a.;) secondly, the 

 foliated character of the margin of the transverse plates, at the junction with 

 the external shell. (PI. 44, Fig. 5, 8, 12, 13.) The external shell of 

 Hamites is also fortified by tran.sverse folds or ribs, increasing the strength 

 both of the outer chambers and of the air-chambers, upon the same princi- 

 ples that we have pointed out in the case of Ammonites. (See Pi. 44, Fig. 

 8,9,11, 12, 13.) 



In certain species of Hamites, as in certain Ammonites, the marginal 

 Siphuncle has a keel-shaped pipe raised over it. Others have a series of 

 spines on each side of the back. (Pi. 44, Fig. 9, 10.) 



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