206 



Bulletin American Museum of Natural History. [Vol. XXXII, 



Diopederma l gen. nov. 



Disk very flat; arms flattened, especially at base, where they are twice as wide as 

 at middle. Disk more or less completely covered with granules. Oral papillae 

 numerous; teeth present, but no tooth-papillae. Arm-spines small and numerous, 

 appressed to side arm-plates. Tentacle scales two. Genital slits small, four in each 

 interradial area, of which two lie close to oral shield, one on each side, and two are 

 dorsal in position, lying just distal to radial shields; these dorsal slits are placed in 

 slight prominences which carry papilliform granules, those adjoining the slits being 

 the longest while the more distant ones merge into the disk granulation; the long 

 axis of each slit is nearly at right angles to the long axis of the arm. 



Type-species. Ophiura daniana Verrill, 1867. Trans. Conn. Acad., Vol. 1, 

 p. 254. From La Union, Salvador. Type in Peabody Museum, Yale University, 

 New Haven, Conn. 



In his description of the type-species, Verrill says: 'The peculiarity 

 in the form and position of the upper genital openings may hereafter require 

 this species to be separated generically from Ophiura, if accompanied by 

 corresponding internal differences in structure." In my judgment, such 

 an extraordinary arrangement of the genital openings, indicating as it does 

 an extreme development of the unusual condition characteristic of Ophio- 

 dcrma, is ample ground for establishing a new genus, regardless of " in- 

 ternal differences," although one can hardly doubt that such a marked 

 external character is accompanied by internal peculiarities. The genus is a 

 most interesting one and I have selected for its type the species described by 

 Verrill, since it is possible that the following species will prove to be identical 

 with it. 



Diopederma axiologum - sp. nov. 

 Plate XLV, Figs. 5-7. 



Disk 16 mm. in diameter; arms 54 mm. long; the smaller specimen is 10 mm. 

 across. Disk pentagonal, very flat, closely covered with a fine granulation (about 

 150 grains to a square millimeter). This granulation leaves uncovered the greater 

 part of each radial shield and the following plates in addition; in the type, a series 

 of three plates along each radius, two lying between the radial shields and the third 

 proximal to them; the first and biggest of these plates is larger than the first upper 

 arm-plate, which lies distal to it; (the second, third, fourth, fifth and sixth upper 

 arm-plates are each successively bigger, until the sixth is the widest of the upper arm- 

 plates, while the succeeding plates are longer but become successively narrower; the 

 first five plates are within the limits of the disk); a series of three or four small 



1 51- = double, 671-17 = a hole in the 

 name of the most nearly allied genus). 

 = remarkable. 



roof, 



skin (the terminal portion of the 



