92 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



Distally the rays have cokimns of small radial pieces, and outside of 

 these are the two supramarginal rows. Proximally between these 

 primary columns there appear accessory pieces, one column of which 

 wedge in between the radials and supramarginals and from one to 

 three between the latter and the inframarginals. In this way finally 

 as many as 13 columns can be counted at the base of a ray. 



The madreporito is situated near the margin between adjoining 

 supramarginal columns, and is conspicuously protruded and large 

 when compared with the small adjacent ossicles. It is a large, 

 radially striate, irregularly circular plate about six times larger than 

 the adjoining pieces. 



MESOPAL^ASTER CARACTACI (Gregory). 

 Plate 9, fig. 6; plate 11, fig. 1. 



Palaeaster caractaci Salter, Cat. Foss. Mus. Practical Geology, 1865, p. 30 (nomen 

 nudum). — Nicholson and Etheridge, Mon. Silurian Foss. Girvan Dist., 

 Ayrshire, fasc. 3, 1880, p. 321 (no description). — Gregory, Geol. Mag., 

 dec. 4, vol. 6, 1899, p. 344. — Schondorf, Jahrb. nassauisch. Ver. Naturk., 

 Wiesbaden, vol. 63, 1910, p. 227. 



Protopalxaster caractaci Spencer, Mon. Brit. Pal. Asterozoa, pt. 1 (Palseontogr. 

 Soc. for 1913), 1914, pp. 21, 30, pi. 1, fig. 5. 



Remarks. — The writer was greatly pleased to receive from Dr. F. 

 A. Bather of the British Museum wax squeezes of the type-specimens, 

 because they clearly show that the genus Mesopalseaster is present in 

 Europe. M. caractaci has its closest relationship in M. shajfferi, the 

 genotype of Mesopalseaster. The differences are easily to be seen on 

 the abactinal side, as illustrated in this work. 



Rays long and slender, abactinaUy flattened. R = 12..5 mm., 

 r = 3.8 mm., R = 3.3r. Radialia small and no larger than the pieces 

 of the accessory columns on either side of them ; the former alternate 

 in position with the pieces of the latter and all of them are more or 

 less spicular in outHne. Basal radials slightly larger than the others. 

 The ossicles of the supramarginal columns large and solid, the most 

 prominent of the abactinal side, very large proximaUy and exceedingly 

 smaU distaUy; there are about 14 in a column. Basal inframarginals 

 most conspicuous of aU abactinal plates, with each pair occupying 

 the axils, and together with the smaller basal radialia form a ring 

 bounding the disk. The disk has fallen in but still shows a few 

 small pointed plates. 



"Madreporito is large, and placed close by one of the interradial 

 angles" (Gregory). 



Inframarginal ossicles almost smooth, large and prominent proxi- 

 maUy, decreasing rapidly in size so that not more than 9 can be 

 seen actinally,. where the tiny pieces pass somewhat over to the 

 abactinal surface, or better the lateral sides; Gregory states that 

 there are 12 in a column. The basal pieces of adjacent columns do 

 not as a rule touch one another in the axils. 



