HAMBACH ANATOMY OF THE GENUS PENTREMITES, ETC. I 59 



Geological formation and locality— In the Kaskaskia limestone 

 of Randolph county and at Chester, Illinois. 



I received this fine specimen through the kindness of Miss 

 Colby, and collected it afterwards in a number of specimens at 

 Chester, Illinois. 



It differs from Pentrcmites robzistus and hemisphericus in be- 

 ing longer than it is wide ; in having the ambulacra! field smaller 

 and depressed, and the poral pieces less in number. 



Pentremites Broadheadi, n. s. (Plate — Fig. 6.) 



Body subovoid. Pelvis large and prominent, forming a very 

 projecting pentangular disc, with five plainly marked surfaces con- 

 verging at the centre. Fork pieces large and heavy ; base por- 

 tion flattened, forming with the corresponding part of the pelvis 

 a lanceolate surface, giving the base an appearance of a 5-sepaled 

 calyx with a projecting crest in the centre of each sepal ; upper 

 portion sloping abruptly from the margin of the ambulacral areas 

 to the separating suture of the adjoining fork piece, thus giving 

 to the interambulacral space a very depressed arrow-head shape. 

 Deltoid pieces small, lanceolate ; their upper acute rostrum pro- 

 jecting above the summit about J^ of an inch. Ambulacral areas 

 very broad and very depressed in the centre. Lancet pieces occu- 

 pying half the field, and concave in a transverse section. Poral 

 pieces thin, counting 9 to yV of an inch. All apertures on the 

 summit rather small and closely arranged. Surface of the whole 

 calyx smooth and not ornamented. 



Dimensions — Vertical height from the acute rostrum of the 

 deltoid piece to the centre of the pelvis li inches ; greatest ti'ans- 

 verse diameter a little above the apex of the ambulacral field ly^g 

 of an inch ; vertical height from apex of ambulacral field to base 

 of pelvis -^^ of an inch ; width of ambulacral field -$^ of an inch, 

 length of same i inch. 



Geological formation and locality — In the Kaskaskia limestone : 

 Evansville, Illinois, very rai^e. 



I named this beautiful fossil in honor of G. C. Broadhead, late 

 State Geologist of Missouri. 



Pentremites basilaris, n. s. (Plate B, Fig. 9.) 

 Body large, conoidal. Pelvis about \ the transverse diameter 

 of the body ; slightly cup-shaped in young but more flat and hori- 



