REVISION OF PALEOZOIC STELLEROIDEA. 89 



So long as the abactinal area of M. (?) parviusculus remains 

 unknown its generic position will be doubtful. For the present its 

 relations appear to be nearest to Mesopalseaster and to M. (?) cata- 

 ractensis. 



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



MESOPAL.EASTER (?) CATARACTENSIS, new species. 

 Plate 9, fig. 2. 



The specimen of this species has been confused with M. (?) gmnti, 

 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, while of M. (?) 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 Mesopalseaster. 



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



The species is most closely related to M. (f) parviusculus, but 

 differs in being larger with more plates in the columns. Of M. (?) 

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

 in each inframarginal column (7 in M. (?) parviusculus) and 

 about 19 in the adambulacrals (13 in M. (?) parviusculus). Then 

 the inframarginals increase very rapidly in size proximally, while 

 in M. (?) cataractensis there is but little 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 M, (?) parviusculus. 



Ambulacral plates unknown. Ambulacral furrows deep, nearly 

 completely closed by the adambulacral columns. 



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. 



MESOPALJEASTER GRANTI (Spencer). 

 Plate 9, fig. 3. 



Palseaster granti SPENCER, Bull. Mus. Univ. Missouri, No. 1, 1884, p. 53, pi. 7, 

 fig. 1. 



Original description. "Body stellate and small with short arms, 

 about 2 centimeters 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 junction 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 highly convex or tuberculi- 

 form plates (the marginal [supramarginal] and ventral [inframarginal] 



