'I AUK.) SALKMA TITMIDlir.A. 41 



TIk' iutoraiiibulaoral areas arc broad, aiul Ibniicd of two alleriiiiliiifjf 

 rows of broad plates, six in each row (PI. x, Fig. \d). The tubercles 

 increase rapidly in size from the moiitli edfjjes, wlierci tlicy are scarc(;ly 

 larger tliau the iiiamillated granules of the ambulacral areas. The 

 areohis are large, and surrounded by mamillated granules of various 

 sizes, that are crowded together along the inner edge of the plates. 

 Between the larger granules are numerous minute granules. The are- 

 ola rises to a prominent boss, that is deej^ly creuulated, and bears an 

 inii>erforate mamclon (PI. x, Fig. 1//). 



The apical disk is very large, convex, subcircular, with radiating 

 ridges that extend from the ovarial openings of each plate and unite 

 with similar ridges of adjacent plates. Small punctures are found at 

 the angles of the jdates and intermediate between thcni (PI, x, Fig. 1//). 

 The subanal plate is situated before the anal opening, and occu])ies the 

 center of the disk. The anal oi)ening is subelliptical, rounded anteri- 

 orly, angular posteriorly, and slightly elevated at the border. 



The under surface is flat and the mouth opening large, covering 

 nearly one-half the diameter of the test. The mouth oijeuing is cir- 

 cular, with ten incisions upon the edge that divide it into nearly equal- 

 sized lobes (PI. X, Fig. Ih). 



Kelated forms. — Oredner, in discussing the affinities of this form, con- ^ 

 siders it to be closely related to Salenia petalifera Defr., and 8. J)esori 

 Wright. It is somewhat more elevated than S. petalifera, and the 

 radial ridges on the apical disk are less pronounced on the latter than 

 on the former. The ocular plates also enter less compactly into the 

 composition of the disk in the latter species. In 8. Desori, on the other 

 hand, there is a wider difference, both in the character of the test 

 plates and the decorations of the apical disk. With *S'. scutigera Gray 

 it also shows some points in common. 



Loealiti/ and geological horizon. — This form is from Cileola, Co- 

 manche spring, Texas, in the Washita formation of the Comanche 

 series (lower Cretaceous). 



Collections. — U. S. National Museum; Boston Society of Natural 

 History. 



Salenia tumidula Clark. 



Plate XI, Figs. la-j. 



Salenia tumidula Clark, 1891. Johns Hopkins T^uiversity Circulars, No. 87, p. 75. 



Determinative characters. — Test small, subglobose; outline of upper 

 surface regularly convex. Ambulacral areas narrow, nearly straight, 

 with two rows of mammillated granules between the pore pairs ; porifer. 

 ous zones slight!}^ flexed; pores unigeminal. Interambulacral areas 

 wide, composed of two alternating rows of live or six plates. Apical 

 disk large, regularly convex, subcircular; anal opening slightly ele- 

 vated. Mouth opening small. 



Dimensions. — Height, ^ inch; transverse diameter, ^ inch. 



