288 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the neighboring part of the tropical Pacific (Lendenfeld, 1903, p. 

 48; 1906, p. 287; Hentschel, 1912, p. 310). 



The shape is recorded as spheroidal, usually oblate (Ridley, 1884, 

 p. 474; Sollas, 1888, p. 116; Topsent, 1897, p. 433; Lindgren, 1898, 

 p. 331; Lendenfeld, 1903, p. 48; 1906, p. 287; Hentschel, 1912, p. 

 310), the diameter ranging from 5 to 14 mm. Only in the case of 

 an isolated specimen, considered by Topsent (1897, p. 433) to be- 

 long to this species, is a different shape recorded. This specimen is 

 a relatively large one, of compressed shape, 45 mm. high, 40 mm. 

 wide, 10-20 mm. thick, exhibiting on its upper border two oscula 

 3-4 mm. wide. Details are not given, except that in the chiasters 

 the rays are tylote or minutely tuberculate. In view of the general 

 uniformity as to shape and size in the species, possibly this speci- 

 men would best be enrolled as a variety. 



The recorded colors embrace 3 T ellowish, greenish white, a pur- 

 plish tint, grayish brown, blackish brown, reddish white. It would 

 seem that the natural color, if at all constant, includes green and 

 purple tints. 



In my specimens, as in the others found (see Sollas, 1888, p. 116). 

 the pores are uniformly distributed in sievelike areas. The ectosomal 

 trabeculae between these areas, which are often about 200 |x wide, 

 contain the clads of the dichotriaenes, the surface appearing reticu- 

 lar. The stratum of small subdermal chambers into which the pores 

 open directly, and which largely fill the ectosome (Sollas, 1888), is 

 present. But I do not find that these chambers are divided by hori- 

 zontal partitions into outer and inner portions (Sollas). From the 

 chambers incurrent canals pass radially into the interior. But these, 

 together with the radial skeletal bundles stop short of the central 

 region, which thus lacks a radiate arrangement. 



Variation in the cloaca. A small cloaca, opening by an osculum 

 in the center of the upper surface, is a characteristic of the species. 

 Sollas gives the most precise statements, but the cloaca described is 

 exceptionally small. (See Lendenfeld, 1906, pi. 29, fig. 7.) He says 

 (1888, p. 117) that the cloaca is in the shape of a short cylindrical 

 tube about 1 mm. deep by 0.725 mm. wide, opening by an osculum 

 surrounded by an oscular membrane. In the accounts of some other 

 specimens it remains uncertain whether a distinct cloaca was present. 

 In Dendy's specimens, for instance, from Ceylon, all small, 9 mm. 

 or less in diameter, there is only " a single, slightly depressed vent " 

 (1905, ]». 72). 



In the great majority of my specimens a distinct though small 

 cloaca is present, opening by an osculum, surrounded by an oscular 

 membrane, which occupies the center of the upper surface; numerous 

 small efferent canals opening into the cloaca. The cloaca is rounded 

 or conical in shape, commonly 2—4 mm. deep, 2-4 mm. wide, the 

 osculum 1-2 mm. wide. The cloaca typically extends inward sym- 



