578 Contributions to Invertebrate Palaeontology. 



base of the arabulacral 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 jjlates ; while above the form is generally rounding or convex. In a 

 basal view the form is pentangular, and viewed from above somewhat penta- 

 lobate ; the ambulacral areas being slightly sulcated. 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. 



The examples observed vary considerable in form according to 

 their relative age, the smaller ones being shorter above than that 

 figured, with narrower areas and shorter poral plates, while the 

 diameter is somewhat less. The species is proportionally broader 

 and shorter than P. ijyriformis Say, although somewhat resembling 

 it, but is sufficiently distinct to be readily recognized. 



Formation and Locality. — In the Maxville limestone (Chester 

 group), at Newtonville, Ohio. Collection of Columbia College. 



MOLLUSCOIDEA. 

 BRYOZOA. 



Genus POLYPOKA McCoy. 



Polypora VarsouvieiisisI 



f Polj/pora Varsouvicnsis Prout, Trans. St. Louis Acad. Nat. Sci., vol. i, p. 237, 

 pi. 15, fig. 3. 



Some macerated fragments of a species of Polypora, very closely 

 resembling this species, have been examined on the surface of thin 

 shaly layers of the Maxville limestones, from Newtonville, Ohio. 

 But the examples are too much worn and too fragmentary for 

 description or illustration. A species of Fenestella has also been 

 detected showing only the nonporiferous surfaces of fragments. 



