402 DESCRIPTIONS OF NEW SPECIES OF FOSSILS, 



Locality and Position. Sage Creek and Great Bend of Missouri River, etc. Fourth 

 division of Section. 



BACULITES GRANDIS, n. sp. 

 PLATE VII. FIG. 1, 2. PLATE VIII. FIG. 1, 2. PLATE VI. FIG. 10. 



Shell elongate ; section varying from ovate to sub-cordiform ; surface of cast marked 

 by very broad and strongly elevated undulations, which commence at the dorsum and 

 pass obliquely downwards, increasing rapidly in size, and, crossing the side of the shell 

 in a broad curve, terminate abruptly on the ventro-lateral region. Undulations less 

 distinct towards the smaller extremity, and finally become obsolete. Septa very deeply 

 lobed, principal divisions scarcely divergent. Dorsal lobe three fourths as long and 

 twice as wide as the superior lateral lobe ; terminated on each side by a narrow elon- 

 gated branch, which is irregularly sinuate and digitate at the extremity. Dorsal saddle 

 shorter and wider than the superior lateral lobe, formed of four branches, the two 

 terminal ones much the larger, and each of them bifid at the extremity by a small 

 sinus ; the whole outline more or less sinuous and the extremities digitate. Superior 

 lateral lobe longer by one fifth than the inferior lateral lobe, narrower than the ventral 

 saddle, divided at its extremity by a deep sinus into two equal parts, which are simply 

 digitate ; above these are two unequal branches on each side ; terminal sinus much 

 deeper than the lateral ones. Ventral saddle longer and about as wide as the dorsal 

 saddle, more deeply divided at its extremity by the auxiliary lobe into two nearly equal 

 branches, each of which is bifid and the extremities digitate, ventral side with three, 

 and dorsal side with two auxiliary branches. Inferior lateral lobe shorter and broader 

 than the superior lateral lobe, divided at its extremity into two nearly equal branches, 

 the one on the dorsal side bifid at the tip and the other digitate, with an auxiliary 

 branch on the ventral side. Ventral lobe as long as the auxiliary lobe of the ventral 

 saddle, but wider at the base, digitate at its extremity. 



Angle of the apex about five degrees. Length, as deduced from the measurement of 

 fragments, by the convergence of the dorsal and ventral sides, five and a half feet or 

 more. Longest diameter of a fragment not distorted by pressure, 3.7 inches ; shorter 

 diameter from the surface of undulations, 3.3 inches ; in the depressions between the 

 undulations, 2.95 inches. 



This species is nearly related to B. ovatus of Say, from which it differs in its much 

 greater size, larger apicial angle, much stronger and more extended undulations, which 

 cross the entire lateral surface of the shell. The section is more obtusely ovate ; the 



