HAMBACH ANATOMY OF THE GENUS PENTKEMITES, ETC. 155 



Geological formation and locality— In the Kaskaskia limestone : 

 at Chester, Illinois, very rare. 



Pentremites nodosus, n. s. (Plate B, Fig. 2.) 



Body SLibovoid, angularly ; the base portion of the calyx below 

 the apex of the ambul^cral areas not quite so long as the part 

 above. Pelvis cup-shaped, and rather large for the size of the 

 specimen in comparison with other species. Fork pieces as long 

 as t of the entire length of the body ; base portion of the same 

 sloping gently towards the upper margin of the pelvis, whereas 

 the upper points of the prongs have a prominent tubercle at the 

 junction with the deltoid pieces. Deltoid pieces small, arrow- 

 head shaped, twice as long as wide, and not projecting above 

 the summit. Ambulacral areas slightly depressed and rather 

 concave. Lancet pieces occupying half the space of the field. 

 Poral pieces small, numbering from 8 to 9 in -^V of an inch. All 

 apertures on the summit rather large, but closely arranged. Sur- 

 face ornamented with fine striag running parallel to the sutures 

 of the plates. Transverse diameter not quite so large as the ver- 

 tical one. 



The tubercles at the junction of deltoid and fork pieces distin- 

 guish this species from Pentremites cervlnus^ which it resembles 

 very much otherwise. 



Geological formation and locality — In the Kaskaskia limestone : 

 Randolph county, Illinois, rare. 



Pentremites abbreviatus, n. s. (Plate B, Fig. 3.) 



Body depressed, conoidal, wider than long ; base portion hori- 

 zontal. Pelvis small and slightly depressed. Fork pieces com- 

 paratively large, with a horizontal base in the same level of the 

 pelvis. Deltoid pieces rather large and not projecting above the 

 summit. Ambulacral areas wide and convex, extending from the 

 base to the summit ; lancet pieces half as wide as the ambulacral 

 field ; poral pieces moderately large, counting 8 to fV of an inch. 

 All apertures on the summit small and closely arranged. Surface 

 smooth and not ornamented. 



Dimensions — Height of specimen \ inch; greatest width at the 

 apex of ambulacral field | inch. 



