NATURAL SCIENCES OP PHILADELPHIA. 275 



Nautilus (Cryptoceras) rookfordensis, M. & W. 



As the only specimen of this shell we have seen consists of not more than 

 half of a volution, we are left in some doubt whether it is a Cryptoceras or a 

 Gyroceras. Its volutions were evidently not embracing, as they are not at all 

 concave on the inner side, but rounded all around, so as to present a slightly 

 oval, or subelliptic section, the transverse diameter of which is to the dorso- 

 ventral, as 132 to 110. The half volution curves around an umbilical cavity 

 apparently rather more than half as wide as the greatest dorso-ventral diame- 

 ter of the volution at the same point. The siphon, although not quite in con- 

 tact with the dorsal side, is so near it as to give the internal cast the appear- 

 ance of having a small deep dorsal lobe. The septa are distant, measuring, 

 on the dorsal side, about two-fifths the dorso-ventral diameter of the whorl 

 at the point of measurement, and their 'edges pass almost directly around 

 the whorls. (Surface, number of whorls and aperture unknown.) 



Length of a half turn, including a small portion of the last chamber, meas- 

 uring around the dorsum, 3-78 inches ; greatest transverse diameter at the 

 larger end, 1-80 inch ; dorso-ventral do., 1-60 inch. 



It is probable, judging from analogy, that the lip of this species, in entire 

 specimens, will be found to be pinched out or projecting laterally on each ven- 

 tro-lateral margin of the aperture, as in some other species of this type. We 

 know of no other species with which it is liable to be confounded. 



Locality and position. Goniatite limestone, of the Kinderhook division of 

 the Subcarboniferous series, at Rockford, Indiana. 



Note. In the August number of the Proceedings of the Academy for 1865, 

 p. 165, we proposed the name Evactinopora, for a curious radiated body, evi- 

 dently belonging to the Polyzoa, from the carboniferous rocks of Missouri. 

 Since that time, farther comparisons lead us to think this fossil possibly 

 not generically distinct from Conodictyum of Miinster. If so, the name of our 

 species will of course become Conodictyum radiatum. It is a little remarkable, 

 however, that the known species of Conodictyum are from Jurassic rocks. 



August 7th. 

 The President, Dr. Hays, in the Chair. 

 Fifteen members present. 



August 14:t7i. 

 The President, Dr. Hays, in the Chair. 

 Fifteen members present. 



August 21st. 

 The President, Dr. Hays, in the Chair. 

 Twenty-two members present. 



Prof. Cope exhibited the remains of a gigantic extinct Dinosaur, from the 

 Cretaceous Green Sand of New Jersey. The bones were portions of the 

 under jaw with teeth, portions of the scapular arch, including supposed 

 clavicles ; two humeri, left femur, and right tibia and fibula, with numerous 

 1866.] 



