466 GEOLOGY OF OHIO. 



Basal plates minute to moderate size, higher than wide. Subradials large ; height 

 and width nearly equal ; two of them heptagonal and the others hexagonal, the 

 lower sides barely divergiug from a straight line. First radials wider than high.and 

 about two-thirds as high as the subradials. Anals visible, three in number; the first 

 elongate pentagonal, nearly twice as high as wide, and situated a little obliquely on 

 the right side of the area ; the other two are small and pentagonal. Second radials, 

 or first arm-plates, smaller than the first radials and narrowing upward, wedge- 

 formed above, and each supporting two arms. On the postero-lateral rays they are 

 long and cylindrical, with the arms slender. On the anterior ray, it is short and sup- 

 ports two slender arms ; while on the antero-lateral rays they support a slender arm 

 similar to those of the other rays on the anterior side, and on the outer side an arm 

 several times larger and stronger than the others, and composed of larger and 

 stronger plates. 



Plates of the arms short and unequal-sided, and giving origin to jointed tenta- 

 culae from the longer side of each plate, which is upon the alternate sides of the 

 arm, or on the same side from every second plate. Surface of the plates smooth. 

 Length of the arms and subsequent bifurcations not known. Column small, round, 

 and composed of unequal-sized plates alternating with each other. 



The slender arms are preserved on two individuals to the length of about one 

 inch, and the strong antero-lateral arm on one, to more than an inch ; but no evi- 

 dence of bifurcation appears. 



The inequality of the antero-lateral arms will be the distinctive 

 feature of the species, as the form of calyx is similar to many other 

 species of the group. 



Formation and Locality. — In the Maxville limestone (shaly portion), 

 at Newtonville, Ohio. 



BLASTOIDEA. 



Genus PENTREMITES Say. 



Pentremites elegans. 



Plate IX, fig. 4. 



Pentremites elegans Lyon, trans. Acad. Sci. St. Louis, vol. 1, p. 632, pi. 20, fig. 4. 



Body small, broadly subpyriform, the length equal to about once and a half 

 the height, but somewhat variable with age ; the greatest width being at the base of 

 the ambulacral areas, or considerable below the middle of the height ; the outline of 

 the lower portion being nearly straight lines, or a little concave between the base of 

 the ambulacral areas and the lower extremities of the basal plates ; while above the 

 form is generally rounding or convex. In a basal view the form is pentangular, and 

 viewed from above somewhat pentalobate ; the ambulacral areas being slightly sul 

 cated. Basal plates small, extending to rather less than half the height of the body 

 below the base of the areas, and in their lower half are somewhat more attenuate 

 than above, the cicatrix for the attachment of the column being very small. Forked 

 plates elongated, and the sinus very broad and deep ; the length of the plates being 

 equal to more than once and a half their greatest width, and their summits slightly 

 truncated for the reception of the small-pointed interambulacral plates, which are 

 in length about equal to one-fourth of the entire length of the areas. Ambulacral 

 areas proportionally wide, distinctly depressed along their middle and composed, in 

 the specimen figured, of about twenty-six pairs of transverse poral-plates, from ten 

 to eleven of which occupy the space of an eighth of an inch in length, in the lower 

 and middle portions, but become shorter above. Summit openings rather large, 

 surface smooth, 



