54 Trans. Acad. Sci. of St. Louis. 



whole length of the body. Genital openings small and close 

 together, appearing on the outer surface as five, of which one 

 is twice as large as the others. This species resembles some- 

 what Pentremites conoideus though it is easily recognized and 

 distinguished from P. conoideus by not having the summit 

 as acute as conoideMs, by its wider ambulacra and by its inter- 

 ambulacral space not being depressed as in conoideus. It is 

 distinguished from Pentremites elongatus by its more conical 

 form, perfectly flat basal portion, having the greatest diam- 

 eter of the body right at the apex of the ambulacrum and 

 not having the interambulacral space finely striated as we 

 find it in Pentremites elongatus. It belongs to the Chester 

 limestone, but has been so far known only from Washington 

 County in Arkansas. 



Pentremites turbinatus n. s. 



Plate v., Fig. 6. 



Body turbinate or inverted pyramidal. Base large for the 

 size of the specimen and funnel shaped. Fork pieces elon- 

 gate, square and large; sinus broad extending down only half 

 the length of the piece. Ambulacrum broad, leaf -like and 

 flat. Poral pieces eleven to one-eighth of an inch. Deltoids 

 externally not visible. Interambulacral space rather flat and 

 smooth. Genital openings close together. Greatest trans- 

 verse diameter at the apex of the ambulacrum which occupies 

 the upper third of the body. 



Geological position and locality: Chester limestone, Evans- 

 ville, Illinois. Very rare. 



Pentremites rusticus n. s. 

 Fig. 15. 



Body almost cylindrical, i. e., the diameter at the base is 

 as great as near the summit. Basal plates very small 

 and not visible in a lateral view. Ambulacra as 

 long as the body with a somewhat rounded surface 

 and sunk into the fork piece sinus which has a 

 sharp and prominent margin. Poral openings 

 Fig. 15. thirteen to one-eighth of an inch. Lateral expres- 

 sion of deltoid one-third of the whole length of the body, 



