170 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



and completely opposite arrangement suggest that T. {?) imhricatus 

 may be an auluroid. Until the original specimen is restudied no 

 definite assignment can be given it. 



MONASTERID^, new family. 



Progressive but primitive five-rayed Cryptozonia, with massive 

 plates, especially the adambulacrals, which are common to the actinal 

 and abactinal areas. Ambulacrals opposite. Interbrachial areas con- 

 sist of a number of pahs of adambulacrals crowded orally Abacti- 

 nally the radial and supramarginal columns consist of large, closely 

 adjoining plates, and are similar to those of Hudsonaster. 



Contains : 



Monaster Etheridge. 



Genus MONASTER Etheridge. 



Palseaster (Monaster) Etheridge, jr. (part), Mem. Geol. Surv. New South Wales, 



Pal., No. 5, pt. 2, 1892, pp. 70, 71. 

 Eiheridgaster Gregory, Geol. Mag., dec. 4, vol. 6, 1899, p. 353 (genoholotype, 



Palxaster clarkei). 



Emended description. — Animal large, very stout, with five thick 

 petaloid rays. Disk very largo, with marked ray angles. 



Abactinal area of rays with prominent radial, and supramarginal 

 columns of large, contiguous, strongly convex, hexagonal plates, 

 densely covered with small granules radially arranged. The ossicles 

 of the radial columns alternate with those on each side and are largest 

 in the mid-length of the rays, decreasing in size both distally and 

 proximally, but most rapidly distally. This growth gives the ray 

 columns a decided petaloid form. Outside of the supramarginals the 

 animal is bounded by single columns of prominent, short, but very 

 wide plates, which are the abactinal aspect of the actinal adam- 

 bulacrals. These plates bear numerous spiniferous tubercles. The 

 ossicles of the axillary disk region are not determinable. In the center 

 of the disk there appear to be five distinct radials and a central disk 

 plate, and around these probably were numerous small accessory 

 pieces, 



Madreporite abactinal, large, oval, radially striate, and situated 

 near the axillary margin. 



Actinally the rays consist almost entirely of the adambulacrals, 

 which are numerous, abundantly tuberculate, short, and very wide. 

 These columns increase rapidly in width, join and form angular 

 axillae, and leave between themselves deep petaloid ambulacral 

 grooves. The interbrachial areas consist of the oral extensions of 

 adjoining columns of adambulacrals, of which there are a great num- 

 ber of pairs, terminating in the mouth in five smaU pairs, the oral 

 armature. 



