white.] PALEONTOLOGY — CRETACEOUS FOSSILS. 315 



volution. Fig. 5 «., plate 7, represents the natural exterior surface, while 

 ■while fig. 5 b represents an exfoliated specimen. 



• Some of the examples show the carinas to be more distinctly raised 

 than they are in either of those that are figured, and less distinctly 

 broken up into nodules. 



The largest example in the collection, when entire, must have had a 

 length of about 6 centimeters and a diameter of last volution, 19 milh- 

 meters. 



This species resembles T. corsicana Shumard, also from Texan Creta- 

 ceous strata ; but it differs from it in some important particulars, among 

 which are its greater number of revolving carinas, which are also less 

 prominent and nodulose ; in its revolving and convex, instead of flat- 

 tened proximal surface of the last volution. It more nearly resembles 

 T. winchelli Shumard, also from Texan Cretaceous strata, but differs in 

 having a greater number of revolving carinas and intervening raised 

 lines, and also in the former being nodulose instead of smooth. The last 

 volution of this species has at least eight carinas, instead of only four, as 

 in T. ■winchelli. 



Position and locality. — Cretaceous strata ; in the vicinity of Helotes, 

 Bexar County, Tex., where it was collected by Mr. G. W. Marnoch, in 

 whose honor the specific name is given. 



TUBRITELLA COALVTLLENSIS Meek. 



Plate 9, fig. 4 a. 



Turritella coalvillensis Meek, 1873, An. Eep. U. S. Geol. Surv. Terr, for 1872, p. 502. 

 Turritella coalvillensis White, 1876, Powell's Eep. Geol. Uinta Mts. p. 98. 



"Shell attaining a large size, elongate-conical; volutions apparently 

 ten or more, distinctly convex, the most prominent part of those of the 

 spire being somewhat below the middle, where they are angular; surface 

 below the angle flattened, or a little concave, and sloping rather ab- 

 ruptly inward and downward to the suture, while above, to near the 

 upper margin, where there is a shallow revolving concavity a little be- 

 low the suture, it is convex ; last volution probably biangular around 

 the middle ; suture well defined ; aperture unknown. Surface orna- 

 mented by rather obscure revolving ridges, about five of which may be 

 counted on each volution of the spire, one being at the lower margin 

 immediately above the suture ; another, which is also the largest, occu- 

 pying the most prominent angular part of the whorl; and above this 

 three others occur, one being above the revolving concavity and at the 

 immediate upper margin; lines of growth obscure and making a strong 

 backward curve in crossing the middle of the volutions. 



"I have not seen specimens of this fine species sufficiently well pre- 

 served to be able to give accurate measurements, though those I have 

 had an opportunity to examine indicate a length of not less than two 

 inches and a fraction, and a breadth of 0.93 inch. The angle of its 

 spire, as taken from near the middle of a large specimen, imperfect at 

 both extremities, measures about 23°, while smaller individuals, com- 

 posed of five or six of the upper volutions, show an angle of nearly 30°. 

 It is, therefore, evidently a large robust species, that increases rather 

 rapidly in size from the apex. 



' i Locality and position. — Coalville, Utah. Prom the Cretaceous, beneath 

 the lower heavy bed of coal." 



This and the five following species are all associated together in the 

 same layer at Coalville, except the third, which is from layers somewhat 



