204 



PALAEONTOLOGY OF NEW-YORK. 



268. 21. ORTHOCERAS LATIANNULATUM (?i. *;).). 



Pl. LIV. Figs. 1 a, i. 



Elongated, cylindrical, anniilated by very strong rounded somewhat oblique ridges, 

 which correspond to the distance between the septa ; septa distant from each other a little 

 less than one third the diameter of the shell ; siphuncle small, excentric ; surface? 



Fig-. 1 a. A fragment, showing four chambers. 1 b. Section and siphuncle. 



We know nothing of the external characters of this shell, having seen only fragments 

 of the casts, which are marked by strong and broad annulations. The siphuncle is com- 

 paratively small, and could never have contained any embryo tube, like the somewhat 

 similar species Endoceras annidatum. 



Position and locality. In the higher part of the Trenton limestone at Middleville. 



269. 22. ORTHOCERAS JUNCEUM ( n. sp.). 



Pl. XLVII. Figs. 3 a, b, c, d, e,f. 



Slender, terete-cylindrical, tapering very gradually ; septa thin, distant from one fourth 

 to one third the diameter ; outer chamber deep ; siphuncle small, central ; section circular; 

 surface finely striated transversely, but without longitudinal striae. 



This species presents a surface marked precisely similar to Endoceras protciforme, var. 

 lineolatum ; but the shell is mucli more slender and gradually tapering, the sipliuncle 

 being always central. The septa, towards the outer chamber, are more closely arranged, 

 sometimes two or three in the usual space of a single one. 



This is a constant species, presenting no important variation in its characters. All the 

 specimens seen are imperfect, and the interior is often filled with crystalline matter, which 

 obliterates the septa and siphuncle. The outer chamber, though incomplete, is proportion- 

 ally very deep. Very little variation in size has been observed in all the specimens obtained. 



Fig. 3 a. A fragment denuded of the shell, showing a part of the outer chamber, and septate portion of 



the tube. 

 Fig. 3 b. A smaller specimen, showing the marks of septa which appear to be slightly oblique. The shell 



covering the lower part of the specimen is crystalline, and preserves no markings upon the 



surface. 

 Fig. 3 c. A small fragment, showing the convexity of a single septum. 

 Fig. Z d. A. section of the last, showing the central position of the siphuncle. 

 Fig. 3 c. A small fragment, showing the closer approximation of the septa near the outer chamber. 

 Fig. 3/ A small fragment, preserving the shell and the striated surface. 



Position and locality. This species is known only in the lower concretionary beds of the 

 Trenton limestone at Watertown, where it is abundant. (Stair Coiieriinn.) 



