48 MESOZOIC ECHINODERMATA OF THE UNITED STATES. [bili..97. 



preliminary report,' wbeu Cyj)hosom9, texanum of the same author was 

 referred to Pscudodiadema. The reference of the latter form to Dip- 

 lo2)0(Iia, in the jireseut report, makes it possible to return to the earlier 

 name for the jiresent species. 



The test is circular, very much depressed ou both the upper and 

 lower surfaces and inflated at the sides (PI. xiv. Fig. Ic). 



The ambulacral areas are narrow and lanceolate. They bear two 

 rows of tubercles, eleven or twelve in each rov7, that decrease rapidly 

 in size from the ambitus to the poles (PI. xiv, Fig. le; PI. xiii. Fig. 26). 

 The areolas are circular, the bosses stout and prominent, the mamelons 

 distinctly perforated (PI. xiv, Fig. Ig). Small secondary tubercles are 

 irregularly dispersed between the rows of primary tubercles. A few 

 scattered granules surround the same. The poriferous zones are uni- 

 geminal throughout, though the pores sliow a slight tendency to in- 

 crease at the peristome. 



The interambulacral areas are about twice the Avidth of the ambula- 

 cral. There are two rows of primary tubercles, nine or ten in each 

 row, that decrease in size from the ambitus to the poles (PI. xiv. Fig. 

 Id; PI. XIII, Fig. 2((). The areolas are depressed, circular, and dis- 

 tinctly outlined, the bosses elevated and deeply crenulated, the mame- 

 lons large and deeply i^erforated. Small secondary tubercles surround 

 the primary tubercles, between which are interspersed minute granules 

 (PI. XIV, Fig. 1/). 



The mouth opening is wide, covering nearly one-half of the diameter 

 of the test. Ten incisions produce Avell-deflned lobes at regular inter- 

 vals (PI. XIV, Fig. lb). The discal opening is large and subcircular, with 

 a deep incision in the right anterior ambulacrum (PI, xiv. Fig. la). 



Related forms. — Both Eoemer and Desor mention the similarity of 

 this species to P. teiiue, of the Cenomanian of Europe, from which, how- 

 ever, it is separated by its smaller tubercles and more numerous gran- 

 ules. 



Locality and geological horizon. — This important species is common in 

 the Fredericksburg formation of the Comanche series (lower Cretaceous) 

 of Texas, and is found at Fredericksburg and near San Saba valley. 



Collection. — U. S. National Museum. 



DIPLOPODIA McCoy. 



DiPLOPODiA TEXANUM (Eocmer). 



Plate XV, Figs, la-f; Plate xvi. Figs. la-d. 



Diadema texanum Roemer, 1849. Texas, etc., p. 392. 



Cyphosoma texanum Roemer, 1852. Die Kreidebildungen von Texas, p. 82, PI. 10, 



Fig. 6. 

 Cyphonovia texanum Conrad, 1857. U. S. and Mex. Bound. Surv. Rept., vol. 1, pt. 2, p. 



145, PI. 1, Fig. 3. 

 Phymosotaa texanum Dosor, 1858. Synopsis des Ecliinides fossiles, p. 90. 



' Johns Hopkins University Circulars, 1891, Ko. 87, pp. 75-77. 



