BLACK-RIVER LIMESTONE. 59 



92. 1. ENDOCERAS SUBCENTRALE (n. s/..). 



Pl. XVII. Fig. 4. 



External form unknown, mucli elongated ; septa rather distant ; siphuncle a large 

 straight subcentral tube, with external iml)ricating elevations at the attachment of the septa. 

 The septa, on approaching the side of the siphuncle, turn suddenly upwards, or towards 

 the apex, before joining the tube. A small portion only of the internal tube is visible, but 

 enough remains to show its character. The marking is too faint to be traced, but it probably 

 differs from any other species in this rock. 



Position and locality. This fossil occurs, associated with the Ormocehas, in the limestone 

 of Black river, at Watertown, Jefferson county. {State Collection.) 



93. 2. ENDOCERAS LONGISSIMUM ( n. sp.) . 



Pl. XVIII. Figs. 1, 1 a. 



Extremely elongated, cylindrical. In the specimen before us, the internal embryo tubes 

 of the siphuncle, only, are preserved : these are cylindrical, elongated, very gradually 

 tapering, each one fitting within the other nearly close at the aperture, but receding from 

 each other towards the smaller extremity ; markings of the surface not visible. 



The section 1 a shows at least three distinct tubes, one within the other, which extend 

 the whole length of the specimen. The portion figured is eighteen inches in length, and 

 this is probably much less than half the whole length of the original. Fragments of this 

 species are very abundant at Watertown, and they are often found embraced within portions 

 of the original shell, which was at least six inches in diameter and several feet in length. 



The two figures connected by a dotted line are parts of the same specimen, joining as 

 indicated. The section 1 a shows the different tubes, one within the other. 



Position and locality. In the Black-river limestone, associated with Ormoceras. Water- 

 town, Jefferson county. (Cabinet of the Albany Institute.) 



94. 3. ENDOCERAS MULTITUBULATUM (n.5;j.). 



Pl. XVIII. Figs. 2 a, b. 



Teretely conical, tapering somewhat rapidly ; embryo sheaths numerous ( five ) , one 

 within the other ; sheaths thin; smooth externally ; interspaces equal, narrow. 



This species differs from the last, in tapering more rapidly towards the apex, and in the 

 consequently different form, as well as in the greater number of sheaths, which latter, 

 however, would not be regarded as important. 



Position and locality. In the Black-river limestone at Watertown, Jefferson county, 

 associated with those forms previously figured. 



