TRENTON LIMESTONE. 211 
276. 8. ENDOCERAS PROTEIFORME, var. LINEOLATUM. 
Pu. XLV. Figs. 4 a, b,c, d,e; Pu. XLVI. Figs. 1 abc, 2ab, & 3; and Pu. XLVII. Figs. 4 a, b,c, d, e. 
Compare Orthoceratites centralis, Hisincrr, Leth. Suecica, 1837, Pl. 9, fig. 4. 
— bacillus, Ercowaup, 1830, Zool. specialis, Vol. ii, pag. 31, pl. 2, fig. 14. 
_ — In. 1840, Sil. Syst. in Esthland, p. 94. 
— linearis, Munster, 1840, Beitr. zur Petrefacten, Heft ili, pag. 99, pl. 19, fig. 1 a, bd. 
— — D’Arcurac & pE VERNEUIL, 1842, Trans. Geol. Soc. London, New series, Vol. vi, 
part 2, p. 345. 
_ bacillus, VerNneEviL, 1845, Pal. Russia and Ural Mountains, pag. 353, pl. 24, fig. 8 a, d. 
This variety is usually more slender than the prevailing forms of the last, but is not 
essentially different. The surface is marked by fine transverse striz, scarcely visible to the 
naked eye ; striae somewhat irregular, lamellose, and crowded into bands or fasciz. The 
siphuncle is equally excentric with the last, and the septa have a concavity of about one 
third their diameter ; section circular. 
The length of the fragment fig. 4, pl. 45, is 45 inches ; the comparative diameters of 
the two extremities are as 4. to 1. In fig. 2, pl. 46, the length is 5} inches, and the two 
diameters as 13 to 3, or about the same as in the other specimen. 
The surface of some specimens, when highly magnified, presents very minute or eva- 
nescent longitudinal strie, approaching in this character to the var. E. tenuistriatum, into 
which it finally passes by a greater development of the longitudinal strie. The transverse 
strie are often imbricating, as if produced by the elevated edges of lamelle which are 
frequently broken or irregular. They also sometimes become vesicular, giving the surface 
a blotched appearance as in fig. 4c, pl. 47. Towards the extremity they often become more 
distinct, and assume the character of sharp annulations. 
This variety differs from the O. centralis of HtstncEr, in the excentric position of the 
siphuncle, and in the finer striz, in which it approaches to O. bacillus, which has likewise 
a central siphuncle and more conical form. 
The finely striated surface of this species is very similar to one or two species in our 
higher strata; but in those the striz are usually stronger, and they do not become, in any 
variety, cancellated in like manner with fine longitudinal striz. It will be desirable, there- 
fore, to recollect these distinctions, in order to avoid confounding what are really distinct, 
and from different geological periods. 
Pirate XLV. 
Fig. 4 a. A young shell, with the outer chamber and apex broken off: This specimen represents the 
prevailing form and dimensions of this variety. 
Fig. 4 b. Transverse section of the larger extremity of 4 a, showing the position of the siphuncle. 
Fig. 4c. A fragment of the smaller extremity of the shell, which is annulated by fine sharp ridges. 
Fig. 4d. The same enlarged. 
Fig. 4 e. A fragment of another tube, marked as fig. 4 a, showing at the lower extremity a septum and 
siphuncle, 
27* 
