134 bulletin: museum of compaeative zoology. 



their yellowish-brown coloration and in the characters of test, spines, and pedi- 

 cellariae. Superficially they look very different from the specimens taken by the 

 " Challenger" at nearly the same place (Station 164 a), which are dull reddish in 

 color and have much stouter spines. 1 do not find, however, any satisfactory 

 specific differences. The Museum now possesses one of the specimens of this 

 species collected by the " Siboga " near Celebes, and one taken by the " Valdivia" 

 near Sumatra, and there seems to be no important difference between them. In 

 size and form, and in length and slenderness of the primary spines, the " Siboga" 

 specimen is remarkably similar to the series of ten from Port Jackson, but it 

 lacks entirely the yellowish-brown coloration. The test is pale dull reddish, and 

 the spines, even secondaries and miliaries, are pure white. 



ECHINOTHURIDAB. 



Asthenosoma thetidis, sp. nov. 



Test rather firm, though greatly flattened in the preserved specimens. Coronal 

 plates, moderately high; in iuterambulacra, about 20 on actinal side and 25 

 abactinally, in a specimen 180 mm. in diameter; in ambulacra there are only 

 about 28 actiually and 42 abactinally. Primordial interambulacral plate at 

 peristome very distinct. Ambulacra wide, nearly three-fourths as wide at ambitus 

 as iuterambulacra. Poriferous areas rather narrow, clearly defined. Primary 

 tubercles abactinally, very few (100-125) and irregularly scattered; actiually, 

 each interambulacral plate carries one or two, but they are arranged in such a way 

 that there are three columns of big tubercles on each side of an interambulacrum, 

 the median area being nearly free from primaries ; most of the actinal ambulacral 

 plates, except those nearest the actinostome, carry a large tubercle near the 

 inner end and a smaller one near the iuterradial end, so that there are four more 

 or less irregular columns of tubercles in each ambulacrum, of which the two 

 median are decidedly the most conspicuous. Secondary and miliary tubercles are 

 comparatively few, and the inner ends of the interambulacral plates, and both 

 ends of the ambulacral plates abactinally, are entirely free from them, so that 

 there are 20 conspicuous, bare areas radiating from the abactinal system to the 

 ambitus. Abactinal system about .17 of the diameter of test; genital plates 

 large (7x7 mm.), roughly triangular, usually not in contact with oculars, but 

 separating the uppermost two pairs of interambulacral plates ; genital openings 

 very large, 3 to 4 mm. in diameter, but confined within the plate ; ocular plates 

 rather small, about 3 mm. wide by 2^ high; anal plates small, widely separated, 

 about 60 in number. Actinostome about .23 of test-diameter, with 13 or 14 con- 

 centric series of ambulacral plates, which diminish so rapidly in size near the 

 teeth that opposite each tooth is a bare, wedge-shaped area 3 mm. wide at base 

 (against the tooth) and about 8 mm. long. Primary spines relatively short, 

 only 15-20 mm. long, even on the actinal surface, where they are tipped with a 

 slender white hoof 3-4 mm. long. Secondary and miliary spines very slender. 

 PediceUariae not peculiar, very similar to those of A. owstoni (Mortens.) ; both. 



