1886.] NATURAL SCIENCES OF PHILADELPHIA. 107 



anal opening in this genus, as a rule, is located between the 

 radials. It either lies directly above the posterior basal, and is 

 followed by a quadrangular or triangular anal plate, or the open- 

 ing is situated above the anal plate. In the former case the two 

 posterior radials may close above the opening, or be separated 

 from one another by additional plates ; the opening may even 

 penetrate exceptionally the posterior basal. Miiller's genus 

 Ceramocrinics, according to Schultze, was founded upon a speci- 

 men in which the anal plate was placed above the opening, con- 

 trary to the typical form of Goldfuss, in which it was below. The 

 name Epactocrinus was proposed for a specimen with very irreg- 

 ular basals, portions of which evidently had been destroyed or 

 fractured, and were restored by the animal, and this ma}^ have 

 produced the irregular form. The construction of the ventral 

 side cannot be satisfactorily ascertained from Schultze's figures. 

 His figs. 1/, and 1 1, on PI. xii, which are said to represent the 

 ventral surface of Gasterocoma antiqua, are so different from one 

 another, that we believe there is a mistake in the figures. These 

 figures diflfer again essentially from fig. 5 6, which is said to 

 represent the same parts in Gasterocoma gibbosa. 



Generic Diagnosis. The lower disk has the form of a 

 pentagon, and extends somewhat beyond the column. It is 

 surrounded by five basals, four of them equal, pentagonal; the 

 fifth larger, hexagonal, truncate above. 



Radials five, pentangular ; three of them are equal, the two 

 next to the az3'gous side irregular. The two latter enclose later- 

 ally not only the anal plate, but also the anal opening, which is 

 surrounded by a single ring of small plates, and either rests upon 

 the truncated upper face of the larger basal, or is separated from 

 the latter by an anal plate. In either case the anus, as a general 

 rule, is succeeded by one or more anal pieces, which, however, in 

 some specimens do not extend to the upper end of the radials, 

 and in tliis ease the radials meet above the anal plates. The 

 radials have a lateral articular facet of the horseshoe form, which 

 extends deeply into the plate. It is notched above for the arm 

 furrow, and pierced by a large axial canal, which is removed far 

 off from the outer edge of the plate. The arms evidently were 

 heavy, and, to judge from the facets, were probably pendent. 



The mouth of Gasterocoma, according to the position of the 

 central piece, was excentric. This central or, as we call it, oral 



