238 
The American Geologist. 
October, 1903 
Comparisons. — This species differs from other Pseudocrin- 
ites, having ambulacra extending to the column by the regular- 
ly oval outline. 
Formation and locality. — Of this species the U. S. National 
Museum has u specimens, Geological Survey of Maryland, i, 
Mr. Gordon, 2, and Mr. Hartley, 10. All are from the quarries 
near Keyser, West Virginia. It gives the writer pleasure to 
name this species for Dr. William Bullock Clark, the distin- 
guished geologist, paleontologist and Director of the Maryland 
Geological Survey. 
Cat. number 35.070, U. S. N. M. 
Pseudocrinites perdewi n. sp. 
The following four specimens represent four stages in the 
growth of this species : 
Brach- 
1 
Length 
Width 
Depth 
ioles 
(Total) 
Rhomb 1-5 i Rhomb 12-1* 
Rhomb 14-15 
Specimen 
Iii6 mm. 
1 1 mm. 
9 mm. 
23 
20 dichop. 
34 dichop. 
40 dichop. 
" 
2 24 mm. 
17 mm. 
12 mm. 
48 
42 
48 " 
58 " 
" 
3|35 mm. 
27 mm. 
15 mm. 
76 
53 
65 « 
82 
4 57 mm. 
39 mm. 
?2Q mm. 
90 
82 
114 
148 
General form pear-shaped with the sides appressed. 
Ambulacra wide, very prominent, with vertical angulated 
sides and flat or slightly trough-shaped oral surfaces. In the 
specimen numbered 1 the two ambulacra taper rapidly and ex- 
tend along the periphery of the theca for one-third the length. 
In number 2, they are just one-half the length, in 
number 3 nearly two-thirds the length, while in number 4 
they are about one-half the length of the theca. This shows 
that the length of mature ambulacra is somewhat variable, 
varying between one-half to two-thirds the thecal length. The 
ambulacrum nearest the anal region is always a little the short- 
er. Number of brachioles on one side of each ambulacrum vary- 
ing with age, there being in the youngest known specimen ( no. 
1) about 5, in a mature individual (no. 3.) about 19 and in the 
largest example (no. 4) about 22. Ambulacral grooves nar- 
row in comparison with the large size .of the parambulacralia, 
and covered by very small rectangular ambulacralia which are 
sharply elevated into a median ridge. There are usually from 
10 to 12 ambulacralia to each parambulacralium, but in different 
