Hambach — Revision of the Blastoideae. 55 



extending near the summit prominently outward, giving to 

 the body a square appearance. Interambuhicral space not 

 depressed as in Pentremiies conoideus and covered with tine 

 striae, running parallel to the sutures. Genital openings 

 small and close together as in the foregoing species. 



Geological position and locality : It occurs in the Chester 

 limestone and is known so far only from Washington 

 County, Arkansas. 



Pentremites kirki n. s. 



Plate v., Fix. 18. 



General form of the body cylindrical, about | of an inch in 

 length and -/g- of an inch in width. Base very robust and 

 funnel shaped, with a large articulation surface for the 

 column, almost as wide as in Codonites. Distance from the 

 articulation surface of the column to the apex of the ambu- 

 lacrum about two-tifths of the entire length of the body. 

 Ambulacra broad and slightly rounded with a yevy coarse 

 plicable integument with only eight plications to one-eighth 

 of an inch. Interambulacral space rather narrow, with a 

 slight depression in the center and a sharp, projecting, spiny 

 crest at the apex of the ambulacrum. Whole surface of the 

 interambulacral space and the base portion ornamented with 

 tine striations, running parallel to the sutures. 



Deltoids hardly visible externally, but the summit projects 

 about yq of an inch above the sharp point of the fork piece. 

 Genital openings, as in Pentremites elongatus or hurlington- 

 ensis where the anterior portion, or the outer septa of the 

 deltoid base, divide each opening in two, while the posterior 

 one is divided into three so that the summit shows very dis- 

 tinctly twelve openings. 



Geological formation and locality : Lower Burlington lime- 

 stone. 



It gives me great pleasure to name this beautiful little 

 Blastoid in honor of Mr. E. Kirk, the lucky finder, who is a 

 very energetic and prominent young collector. 



