34 PROCEEDINGS OF THE ACADEMY OF 



furrows well denned, and also minutely crenate. Central hiatus small. So- 

 called ovarian openings small, and those distinct from the anal opening ap- 

 pearing at the surface as four pairs of closely approximated elongate-oval 

 pores. Anal opening comparatively large, and, as usual in the genus, inclu- 

 ding one of the pores on each side. Surface ornamented with five parallel 

 strise, running as usual in allied species. 



Height of one of the smaller, less globose specimens, exclusive of the little 

 supplementary base, 0-50 inch ; breadth, 0-49 inch. Height of a large, more 

 ventricose specimen, 0-87 inch ; breadth of do., 0-84 inch. 



This species has much the form and general appearance of the common P. 

 Godoni, so mueh so, indeed, that those who give wide limits to species 

 would probably fail to observe any well defined differences. Ou comparison, 

 it will be found to differ, however, in the following characters, viz. : In the 

 first place, its pseudo-ambulacral areas are more convex, and not bounded by 

 near such sharply elevated margins of the radial pieces. Its pore pieces are 

 also larger, and scarcely more than half as numerous as in P. Godoni. Its 

 anal and interradial pieces are likewise decidedly smaller than in that species, 

 while it also presents the well-marked difference of having its so-called 

 ovarian openings with each pair appearing at the surface, as two closely ap- 

 proximated, but distinct elongate-oval pores, instead of as a single round, 

 larger opening. It moreover holds a much lower geological position than P. 

 Godoni. 



It is the first true, typical Penlremitewe have seen with each pair of ovarian 

 pores (so-called) appearing as two distinct pores at the surface. It must be 

 quite rare, as only three specimens have come under our observation. 



Locality and position. Upper division of the Burlington group of the Lower 

 Carboniferous, at Burlington, Iowa. No. 387 of Mr. Wachsmuth's collection. 



Oligopoeus Coreyi, M. and W. 



Body small, subglobose, or apparently depressed-globose, and deeply sul- 

 cate ; composed of moderately thick plates; apical region sunken. Inter- 

 ambulacral areas twice as wide as the ambulacral, very convex, and rounded 

 over from side to side ; composed at the middle by six ranges of plates, which 

 decrease in numbers to apparently about three ranges, at the upper and lower 

 extremities of the areas. Ambulacra! areas deeply furrowed along each side, 

 and rising into a rather prominent ridge along the middle ; composed of 

 somewhat irregular plates, as to size and form, but clearly showing but two 

 rows ou each side of the mesial zig-zag suture, the outer range being gener- 

 ally a little shorter in the transverse diameter than the inner ; the two pores 

 of each piece situated near its outer end. Apical disc unknown. Oral aper- 

 ture, as seen in the test, comparatively large. Surface unknown. 



Height, as near as can be determined fiom a somewhat distorted specimen, 

 about 1-65 inches ; breadth near 2 inches. 



This species is most nearly allied to O. Dance, but differs not only in being 

 much smaller, and apparently more depressed in form, but in having much 

 more deeply furrowed ambulacral areas, and only six rows of interambulacral 

 pieces at the widest part of the areas, instead of eight, the plates being also 

 larger in proportion to the size of the bod}'. 



From our O. nobilis it will also be readily distinguished by its much smaller 

 size, and more deeply sulcate ambulacral areas, which are also proportionally 

 much wider. It also differs in having six rows of interambulacral pieces at 

 the widest part of each area, instead of only five. 



Locality and position. Crawfordsville, Indiana; from the Keokuk division 

 of the Lower Carboniferous series. The specimen from which the description 

 was made out belongs to Mr. Corey, of Crawfordsville, Ind.. to whom we have 

 dedicated the spechs. 



[April, 



