HAMBACH ANATOMY OF THE GENUS PENTREMITES, ETC. 157 



Pentremites clavatus, n. s. (Plate B, Fig. 5.) 



Body elongated, clavate, having its greatest diameter at the apex 

 of the ambulacral field. Pelvis rather small, cup-shaped. Fork 

 pieces long ; incision for the reception of ambulacral field as long 

 as the base portion below, so that the distance from the apex of 

 ambulacral field to the base of pelvis is | more than that of the 

 portion above. Deltoid pieces very small, externally not visible, 

 and their acute angles do not reach the summit ; so that the 

 ambulacral fields at the summit will join each other for a dis- 

 tance of about jij of an inch. The general shape of the upper 

 part of the calyx is a nice oval, whereas the lower portion as- 

 sumes a triangular shape, due to the flattening at the base of 

 three fork pieces in their median line. Ambulacral fields mod- 

 erately wide, and about as long as f of the entire length of the 

 body. Lancet pieces half as wide as the ambulacral field. Poral 

 pieces large, amounting to 7 in y^ of ^" i"'^^''- Mouth central, 

 round ; the ovo spiracle apertures somewhat closely arranged, 

 and rather large for the size of the specimen. Articulating sur- 

 face for the column large and round, measuring ^ of an inch in 

 diameter. 



Entire length of specimen il inches, greatest transverse diame- 

 ter j^g of an inch. 



Surface apparently not ornamented. 



Geological formation and locality — In the Kaskaskia limestone : 

 Evansville, Illinois, rare. 



Pentremites hemisphericus, n. s. (Plate B, Fig. 7.) 

 Body large, hemispherical. Pelvis large, forming a shallow 

 cup and occupying nearly ^ the width of the body ; pieces forming 

 the same convex in the centre, giving the cup three longitudinal 

 depressions parallel to the sutures. Fork pieces large ; base por- 

 tion of same horizontal, forming almost a rectangle with the ver- 

 tical diameter of the body ; upper portion sloping gently from the 

 margin of the ambulacral areas to the separating sutures of the 

 adjoining fork piece, giving thus a more even surface to the inter- 

 ambulacral space. Deltoid pieces large, h the entire length of the 

 body, and not reaching the summit for the distance of about 3 or 

 4 poral pieces. Ambulacral fields broad and slightly depressed 



