Contributions to Pakuontology. 33 



to each plate. Each scar consists of a central mammillary elevation, 

 surrounded b}- an elevated ring, which resembles the attaching base 

 for a spine; but there is some evidence that the inner rim was pierced 

 forming a connection between the canal surrounding the mammillary 

 elevation and the interior of the disk, anct we have no idea 

 that the animal had spines upon this rim. 



The inner or submarginal rim does not appear on the upper surface 

 to have ever been connected from plate to plate, but to consist of twen- 

 ty disunited pieces. The interior of this inner rim has a semicircular 

 groove, which was the place of connection with the interior disk. The 

 upper surface of the inner or submarginal rim, in good specimens, is 

 strongh' tuberculated. 



In other words, we would describe this ring as consisting of twenty 

 somewhat quadrangular plates, having a semicircular groove on the 

 interior side, an elevated inner rim, disconnected on the upper surface, 

 but probably united b}^ a tubular channel, and strongly tuberculated, 

 and an outer marginal rim, having mammillary elevations, surrounded 

 by canals which are connected with the semicircular groove on the in- 

 terior side by small pores penetrating the inner rim. 



The specimen figured was found in the upper part of the Cincinnati 

 Group, near Morrow, Ohio, and is now in Mr. Dyer's collection. 



Cyclocystoides minus, n. sp. (Plate II., fig., 5.) 



['E.iy.— Minus, small.] 



This is a flat circular ring, composed of nineteen plates. .The speci- 

 men is weather-worn, and pressed a little out of shape, and is in Mr. 

 Dyer's collection. The groove on the interior side of the plates is 

 distinct. The outer rim is destroj'ed, and a groove is left on the inner 

 rim, where the pores, which connected the outer rim with the interior 

 semicircular groove, are quite distinct. The specimen is about 3-lOths 

 of an inch in diameter, and was found near Morrow, Ohio, in the upper 

 part of the Cincinnati Group. 



Cyclocystoides parvus, n. sp. (Plate II., fig. 6.) 



[^.ty— Parvus, little.] 



This species consists of twenty-six marginal plates, and is about 

 four tenths of an inch in diameter. It is a weather-worn "specimen, 

 from Mr. D3^er's collection, and is pressed a little out of its circular 

 form. Only enough of the interior part of the ring is preserved, to 

 enable us to count the plates. It was found near Morrow, Ohio, in 

 %e upper part of the Cincinnati Group. 



