860 THE PALEONTOLOGY OF MINNESOTA. 



[Oyrtolltes ornatus. 



which should not be the case in a true Oxydiscus. Perhaps it would be better to 

 place the last species, together with C. euryomphalus Lindstrom, into our new genus 

 Cyrtolitina, which is more especially intended for the reception of four other Gotland 

 shells described by Dr. Lindstrom as Cyrtolites lamellifer, C. pharetra, C. arrosus and 

 C. obliquus. 



. CYRTOLITES ORNATUS Conrad. 



PLATE LXII, PIGS. 27-31. 



Cyrtolites ornatus CONRAD, 1838, Ann. Geol. Rept. N. Y., p. 118; Ibid. (1839), p. 63; Ibid. (1841), p. 37. 

 VANUXEM, 1842, Geol. Rept., p. 65, fig. 2. EMMONS, 1842, Geol. Rept., p. 

 402, fig. 2. HALL, 1847. Pal. N. Y., vol. i, p. 308, pi. LXXXIV, figs. \a-g. 

 MEEK, 1873, Pal. Ohio, vol. i, p. 148, pi. xm, flgs. 3a, b. MILLER, 1874, Gin. 

 Quart. Jour. Scl., vol. 1, p. 308. And of many other authors. 



Shell varying in diameter between 12 mm. and 30 mm., with the average at 

 about 23 mm. Volutions two or three, rapidly increasing in size, strongly and 

 sharply carinate dorsally, rhombic subquadrate in section; sides prominent and 

 subangular or narrowly rounded along a line about three-fifths of the hight of the 

 volution within the dorsal carina, the dorsal slopes gently convex and distinctly 

 undulated by strong slightly curved transverse furrows and subangular ridges, the 

 ventral or umbilical slopes almost flat and usually without undulations; ventral side 

 with a sharp central furrow for the reception of the dorsal carina of the preceding 

 volution. Umbilicus well defined, wide and deep, the edge wavy. Aperture a little 

 wider than high, the hight equalling usually a trifle more than half the greatest 

 diameter of the shell, more or less rhombic-subquadrate, the outline often becoming 

 a little rounded with age. Entire surface covered by a delicate network formed of 

 raised lines running almost straight across the whorls and short connecting lines 

 arranged alternately, the result being somewhat similar to the pitting of a thimble. 

 In a good light the network is generally distinguishable without the aid of a magni- 

 fier, and, excepting three specimens, quite uniform in strength in different shells, 

 there being on the outer half of the last whorl nearly always seven or eight of the 

 transverse lines and eight or nine of the short lines in 2 mm. In the excepted 

 specimens the network is more compact, there being over the outer part of the last 

 whorl from ten to twelve of the transverse lines in the same space. On another, 

 with the reticulation unusually coarse, the number averages between six or seven. 

 On the last specimen a good magnifier brings out some very fine lines of growth 

 running through the network. It is important to note that there is no perceptible 

 backward curvature of the transverse lines in nearing and crossing the dorsal 

 carina. 



The above description applies to the species as it occurs in the groups of the 

 Cincinnati period wherever these are exposed in the United States and Canada. In 



