EASTERN TROPICAL PACIFIC ASTEROIDEA. 83 



by me in 1913 (Bull. Amer. Mus. Nat. Hist., 32, p. 192). The number of adam- 

 bulacrals in ]3roportion to ten inferomarginals is either nine or ten, while the 

 number of adambulacral spines is from six to eight, and there are from five to 

 eight spines on the \'entral surface of the plate. On the other hand the project- 

 ing angle of the adambulacrals is not near the aboral end of the plate, but in 

 the larger specimen is about at the middle and in the smaller is distinctly adoral. 

 Probably these details of the adambulacral plates show considerable diversity 

 in the species. 



The armature of the superomarginal plates in the present specimens some- 

 what resembles that of P. dissonus for from four to eight of the granules on the 

 outer (lower) end of the superomarginals in the interbrachial arc are more or less 

 elongated into flattened, bluntly pointed spinelets. But these spinelets do not 

 seem to be encased in "membranous sheaths" nor are they as long as in typical 

 dissonus. 



Station 4654. Peru: off Aguja Point, 24 miles, 1,036 fms. Bott. temp. 37.3°. Dk. br. m. 



Two specimens. 



Litonotaster tumidus,' sp. nov. 

 Plate 3, fig. 3-6. 



R = 28 mm.; r = 14 mm.; R = 2 r. Disk pentagonal, the arms arising 

 quite abruptly from the angles. Br. = 6 mm. at base and nearly 2 mm. just 

 before tip. In some specimens, the body is not noticeably pentagonal, the inter- 

 brachial arcs being very weU-rounded. Thus in a specimen with R = 27 mm., 

 r = 11.5 mm. and br., at the level of the interbrachial arcs, 11 mm., the form 

 is quite evenly stellate. In all cases however, the disk is more or less swollen; 

 in the holotype, the vertical diameter at center of disk is 11 mm. while at the 

 margin the thickness is only 3.5 mm. 



Abactinal surface covered by numerous circular or rounded-polygonal, 

 thin plates, .5-1 nmi. in diameter, not very fii'inly united together and hence 

 forming a flexible covering. In each interradius but one, is a circular plate, 

 evidently larger than its neighbors, about 1.3 mm. across; in the fifth interradius 

 is the madreporite, a somewhat tumid, rounded-triangular plate, 1.5 mm. 

 across, adjoined on each of its three sides by a plate about 1 mm. wide and .75 

 mm. high. Excepting the madreporite, these interradial plates are discernible 

 only in dry specimens. In each radius, at the base of the arm, is a group of 



1 tumidus = swollen, in reference to the flexible, puffed upper surface of disk. 



