REVISION OF PALEOZOIC STELLEKOIDEA. 89 



So long as the abactiiial area of 21. {?) parviusculus remams 

 mIl^:no^^^^ its generic position will be doubtful. For the present its 

 relations appear to be nearest to Ilesopalseaster and to M. {?) cata- 

 ractensis. 



Cat. No. 60620, U.S.N.M. 



MESOPAL^ASTER (?) CATARACTENSIS, new species. 

 Plate 9, fig. 2. 



The specimen of this species has been confused with M. {?) granti, 

 from which it differs in being smaller and in having far fewer plates 

 in the columns. The actinal side of M. (f) cataractensis alone is 

 known, whib of 21. {?) granti only the abactinal, but even so the 

 above comparison can still be made because the size of plates is 

 relatively about the same in species of Mesoimlxaster. 



Measurements: R, = 9 mm., r=3 mm., E, = 3r. 



The species is most closely related to 21. (?) imrviusculus , but 

 differs in being larger with more plates in the columns. Of 21. (f) 

 cataractensis only the actmal side is known, with 12 to 13 plates 

 in each inframarginal column (7 in 21. (?) iMrviusculus) and 

 about 19 in the adambulacrals (13 in 2£. (?) imrviusculus) . Then 

 the inframarginals increase very rapidly in size proximally, while 

 in 2£. (?) cataractensis there is but Httle enlargement. 



A single small, pentagonal, axillary interbrachial plate occurs 

 in each area immediately beneath the basal inframarginals. These 

 are much smaller relatively than those in 21. (?) imrviusculus. 



Ambulacral plates unlmown. Ambulacral furrows deep, nearly 

 completely closed by the adambulacral colunms. 



Formation and locality. — In the base of the Siluric (Cataract for- 

 mation) at Hamilton, Ontario. The holotype was found by Mr. 

 Elliott near the city reservoir and is in the collection of the Hamilton 

 Natural History Society. It was loaned to the writer by the late 

 Col. Charles Coote Grant. 



MESOPAL^ASTER GRANTI (Spencer). 



Plate 9, fig. 3. 



Palxaster granti Spencer, Bull. Mus. Univ. Misaoiiri, No. 1, 1884, j). 53, pi. 7, 

 fig. 1. 



Onginal description. — "Body stellate and small with short arms, 

 about 2 centuneters across; disk less than 1 centimeter wide, and 

 apparently formed by the junction of the rays; rays 5 millimeters 

 wide at base, tapering slowly, and terminating in rounded extrem- 

 ities, at about 8 millimeters from jmiction of their base with the 

 disk; upper surface of rays composed of 5 [not less than 9 in mature 

 specimens at mid-length of rays] ranges of liiglily convex or tubercidi- 

 form plates (th(^ marginal [supramargLnal] and ventral [inframarginal] 



