392 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



.sinuous on each lateral margin, convex in outline on the antisiphonal side 

 (ventral of some), and extended into a linguiform, or more or less angular, 

 projection on the siphonal side, very rarely sinuous on the antisiphonal mar- 

 gin, with tin; projection of the siphonal side curved over the aperture; sur- 

 face nearly smooth, or marked with strife of growth, costas, or ridges, and 

 sometimes with nodes, the stria 1 and costse, or ridges, corresponding more or 

 less nearly to the curves of the margin of the lip ; septa symmetrically 

 divided, nearly always into six principal lobes and six sinuses,* all of which, 

 excepting the antisiphonal lobe, being provided with paired branches ; 

 siphonal lobe generally a little shorter than the first lateral lobe : antisiphonal 

 lobe small, and nearly always tripartite, or tridigitate at the end. 



As usually understood, this genus seems to me to be divisible into at 

 least two or more marked subgenera, or probably two distinct genera. These 

 sections may be separately defined as follows: 



1. baculites, Lamarck (typical.) 



a. Shell straight throughout; aperture directed forward; lip 

 with lateral sinuses directed backward ; the projection of its siphonal 

 margin straight, and its antisiphonal margin convex in outline; inte- 

 rior without regularly-disposed ridges. — (Type as already stated.) 



'. /). Shell straight posteriorly, but with the non-septate part 

 gently arcuate; aperture a little oblique; appendage of siphonal side 

 of lip arching slightly with the general curvature of the non-septate 

 part, but not curving over the aperture. — [B. incurvatus, Dujardin.)f 



2. cyrtochilu Meek.J 



Shell straight : aperture opening toward the antisiphonal side, 

 and the lateral sinuses of the lip excavated in the opposite direction ; 

 projection of siphonal margin of lip abruptly arching over the aper- 

 ture, and the antisiphonal margin of same deeply sinuous instead of 

 convex in outline ; interior with regularly-disposed ridges, leaving 

 oblique constrictions on internal casts. — (Hamites baculoides, Mantell {= 

 Baculites obliguatics, Sowerby).) 



* />'. Neocomientis, d'Orbigny, lias only four lobes and four sinuses to each septum : while /;. laby- 

 riiithiius, Morton, according to a figure published by Mr. Gabb, has eight lobes and eight sinuses to each 

 septum. These, however, are rare exceptions to the general rule, 



t Since this was written. I have examined a specimen of Samitus arculas, Morton, from Alabama, 

 a ml find from the curves of its lines of growth, that the outline of its lip agrees nearly with the lip of 

 this section, and differs entirely ftom the outline of the lip m Samites. Consequently, I would refer it to 

 this section of the genus Baculites, 



i Kvproc, curved ; | >/';>■■ , lip. 



