194 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



COMPSASTER, new species. 



Professor Weller collected an excellent asterid at Fountain Creek, 

 Waterloo, Illinois (No. 14395, University of Chicago collection), 

 showing the entire actinal side of a form that is nearest to O.formosus. 

 It is, however, a smaller and more slender species, but until the 

 abactinal surfaces of both species are known, one can not say that 

 they are certainly of the same genus. 



Measurements : R = 20.5 mm., r = 4.5 mm. 



SCHUCHERTIID^E, new family. 



Specializing Cryptozonia with well-developed pentagonal inter- 

 brachial arcs. Inframarginals well developed in the proximal regions 

 where they remain adjoining the adambulacrals. Interbrachial 

 and abactinal areas composed of small, more or less closely adjoining 

 plates without regular arrangement. 



Madreporite unknown. 



Contains : 



Schuchertia Gregory. 



Remarks. This family is the most ancient and primitive of all 

 large-disked or pentagonal starfishes devoid of marginals. In 

 Schuchertia the first appearing inframarginals are retained through- 

 out life and remain adjoining the adambulacrals in the axillary 

 regions. These columns distally become less distinct and in the 

 outer third of the rays are not distinguishable as inframarginals 

 from the other smaller ossicles of the interbrachial areas. This 

 therefore indicates that during the growth of Schuchertia the infra- 

 marginals are in the process of elimination and in later forms seem 

 to be completely disguised or lost. Then the plates of the inter- 

 brachial and abactinal areas, while small, are usually strong, rarely 

 spicular or stellate but never decidedly so, while in later genera the 

 ossicles either break up into smaller and smaller plates, even into 

 granules, or are spicular or thorny pieces. Even the adambula- 

 crals which are well developed in Schuchertia may become greatly 

 modified and almost eliminated. 



In seeking for an ancestor for this family, it is plain that it came 

 from a stock like Hudsonaster. This genus actinally has columns 

 of ambulacral, adambulacral, and inframarginal plates; abactinally, 

 inframarginal, supramarginal, and radial columns of plates. In 

 addition there are five axillary marginals, and on the disk a ring of 

 five basal radial and five interradial plates giving rise to the radial 

 and supramarginal columns. The first step from Hudsonaster toward 

 Schuchertia would be a form of the former genus introducing small 

 ambital plates. This type is as yet unknown, but is suggested in 

 UrastereTla. The progressive introduction of ambital plates and no 



