86 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



their ends together in such manner as to make an angular gutter 

 [the plates of adjoining columns are arranged practically opposite]. 

 The length of these plates is three times as great as the diameter. 

 The plates are placed with the length across the rays. There are 

 15 plates on each side of the groove in each ray, in the length of one 

 quarter of an inch [this is an error as there are about 20 plates in a 

 column]. The diameter of the body is tliree-tenths -of an inch. 



"This species is founded upon a single specimen, in Mr. Dyer's 

 collection, which shows only part of the ventral side. The ends of 

 the rays [most of the adambulacrals] and marginal plates are destroyed 

 [each axillary area appears to bear one axillary interbrachial plate]. 

 The parts preserved seem to distinguisli it from any species hitherto 

 described." 



Formation and locality. — In the original description the locahty 

 is given as Cincinnati, Ohio, but the character of the rock shows that 

 it is from the uppermost portion of the Trenton limestone, probably 

 opposite Cincinnati, in the river quarries at Ludlow, Kentucky. 

 The type (No. 25) is in the J^useum of Comparative Zoology, Harvard 

 University. 



Remarks. — This specimen preserves well the very wide ambulacrals 

 but almost no other plates. The adambulacrals are nearly all removed 

 and but very little is to be seen of the marginals. In three of tlie 

 axillary areas there are single interbrachial plates, one of the essential 

 features of Mesopalseaster. It is referred to this genus provisionally, 

 as nothing is known of the abactinal side. 



MESOPAL^ASTER (?) ANTIQUUS (Troost). 



Asterias anliqua Troost (not Hisinger 1837), Trans. Geol. Soc. Penn., vol. 1, 1835, 

 p. 232, pi. 10, fig. 9; Proc. Amer. Assoc. Adv. Sci., vol. 2, 1850, p. 59 (cat. name). 



Petraster (?) antiqua Shumard, Trans. St. Louis Acad. Sci., vol. 2, 1866, p. 386 

 (catalogue name). 



Palxaster (Argaster) antiqua Hall, Twentieth Rep. N. Y. State Cab. Nat. Hist., 

 1868, p. 287; rev. ed., 1868=1870, p. 329. 



Palseaster antiquus Miller, N. Amer. Geol. Pal., 1889, p. 265 (cat. name). 



Argaster antiqua Gregory, Geol. Mag., dec. 4, vol. 6, 1899, p. 345 (gen. ref.). 



Palxaster antiqua Wood, Bull. U. S. Nat. Mus., No. 64, 1909, p. 105, pi. 8, fig. 1. 



Although tliis is the first recorded American fossil starfisli, very 

 little is known about it and that httle is mostly of a misleading nature. 

 The specimen hes on a limestone slab and is very badly weather- 

 worn or it may have been treated with hydrochloric acid so that now 

 it is nothing more than a polished section of a starfish. An illustra- 

 tion that will sliow its actual characters can not be made. 



Professor Hall errs in stating that Asterias antiqua has " ambu- 

 lacra] grooves occupied by a single row of subquadrate ossicula, which 

 extend across and alternate with the adambulacral plates of each mar- 

 gin. * * * It is possible that this character may prove to be 

 of generic importance." It may have been this character on which 



