288 
Aug. F. Foerste 
is there any evidence of the individual plates being hollow and 
there scarcely is room for such a hollow space between the exterior 
and interior surfaces of these plates. The general form of the 
specimens is subglobose, more or less depressed, with a depression 
on that side usually regarded as the base. The stellate grooves 
were first described and figured by Joseph F. James, the son of the 
original describer, and one of the cotypes preserving these features 
to a marked degree is here illustrated. 
Similar stellate markings have been found on the exterior sur- 
face of the plates in specimens of Pasceolus darwini Miller, at the 
base of the Bellevue member of the Maysville, 2 miles south of 
Maysville, Kentucky, along the railway. In fact, stellate markings 
occur on a plate preserved on one of the cotypes of this species at 
present in the Faber collection at Chicago University, and obtained 
at this locality and horizon. This series of cotypes is numbered 
8838, and is assumed to include also the specimens figured in the 
original description of Pasceolus darwini. 
In his original description of Pasceolus darwini (1874, Cincin- 
nati Quart. Jour. Sci., 1, p. 5, figs. 1, 2), Miller states that frag- 
ments and poor specimens occur also on the hills back of Cincinnati, 
at an elevation of about 400 feet above low water mark. This 
may correspond to the Bellevue horizon, Pasceolus tumidus having 
been described by James from about 350 feet above low water. 
An examination of numerous specimens of Pasceolus from the 
middle of the Maysville in Kentucky and Ohio suggests that Pas- 
ceolus darwini, Pasceolus claudei, and Pasceolus tumidus all belong 
to the same species. They all contain from 15 to 17 plates along a 
line drawn transversely across the so-called upper surface of the 
specimen, indicating that from 30 to 35 of these plates should occur 
along a great circle surrounding the subglobose specimens. From 
this it is evident that difference in the size of the plates is due to a 
corresponding difference in the size of the entire specimen, and 
suggests a difference in the stage of growth of the individuals, 
rather than a specific difference. In a similar manner, only the 
larger specimens, from 25 to 30 millimeters in diameter usually 
present the distinct but rather shallow depressions on that side 
usually regarded as the base of the specimen, while specimens from 
20 to 25 millimeters in diameter usually show only a faint trace * 
of this basal depression, and on still smaller specimens this depression 
usually is absent. 
