TRENTON LIMESTONE. 
201 
263. 16. ORTIIOCERAS CLATHRATUM ( n. sp.). 
Pl. XLIII. Figs. 4 a, b, c. 
Compare Ortboceratites umhilatus, Hisinger, Leth. Suecica, 1837, pag. 28, pl. 10, fig. 2. 
Cylindrical, gradually tapering, marked by moderately elevated subangular annulations, 
longitudinally marked by sharp elevated lines distant of an inch in the specimen figured; 
between and crossing these longitudinal lines are still finer transverse lines or striae, one 
third the distance of the longitudinal ones ; section circular ; siphuncle 1 ? 
I have seen but the small fragment of the fossil here figured, but it is quite distinct from 
any other species in its surface markings. The transverse ridges are angular, and distant 
about one half the diameter; the longitudinal lines are at equal distances, sharp and 
prominent; the transverse striae are stronger and more clearly marked than in the preceding 
Species, and distinctly cross the longitudinal ones, producing finely crenulated edges. 
Fig. 4 a. The fragment, natural size. b. Magnified portion of the surface, c. Transverse section. 
Position and locality. In the lower shaly limestone at Middleville. 
264. 17. ORTHOCERAS VERTEBRATE ( n. sp.). 
Pl. XLIII. Figs. 5 a, b, c. 
Cylindrical, very gradually tapering, annulated with abruptly elevated angular ridges, 
which are distant from each other about one fourth the diameter of the tube, slightly arched 
upon the back, and direct on the ventral side ; surface marked by strong longitudinal striae 
and finer transverse ones, giving it a cancellated appearance ; siphuncle apparently central 
or subcentral. 
The specimen figured is somewhat compressed, scarcely diminishing towards the apex. 
The septa are not visible, though there is some evidence of a siphuncle at one extremity. 
This species differs from any of the preceding ones, in the abruptly elevated and angular 
annulations, which are comparatively more distant from each other, and but slightly 
arched upon the back. The tube is more gradually contracted towards the apex, and the 
annulations less arched upon the back. In this respect it resembles a species in the higher 
strata, but is otherwise very distinct from it. 
Fig. 5 a. Ventral side of the fragment. 
Fig. 5 b. Portion of the dorsal side, showing the slightly arched annulations. 
Fig. 5 c. Transverse section of the specimen. 
Position and locality. In the compact limestone at Middleville. (From Mr. Wadleigh.) 
j Paleontology.] 
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