42 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the adult is indicated only in a fimbriate channel between the 2 

 series of superomarginal plates. One or 2 superomarginals have 

 a special dorsal spine. 



The epiproctal peduncle is prominent, and there is certainly a tiny 

 pore at the summit. Whether this is confined to immature life can 

 not be determined. 



Actinal intermediate areas with well-spaced, small spinelets. 

 Adambulacral plates longer than wide with a palmate series of 5 

 flattened pointed furrow spinelets disposed along the obtusely angu- 

 lar margin, and basally webbed. Subambulacral spinelets, small, 1 

 or 2, or absent. Mouth plates with 8 marginal spinelets; suborals 

 few, rudimentar5^ 



These young specimens resemble the genus Hyphalaster^ more es- 

 pecially H. hyalinus Sladen. They differ from this genus, however, 

 in having cribriform organs between all the marginals. Hence the 

 number of organs is determined by the number of marginals. It is 

 important to note that a certain strongly marked character of the 

 adult, and one which is believed to be generic, is only partly de- 

 veloped in these immature examples. I refer here to the peculiar 

 distribution of the cribriform organs, which in the interbrachium 

 are fused into one in the adult, and also occupy the dorsal radial 

 area of the distal portion of ray. In the adult the terminal plate is 

 entirely dorsal to the superomarginals but in the young only the 

 proximal half overlies the distal superomarginals. 



With only the young specimens, it would not be possible to cor- 

 rectly diagnose the genus Benthogenia. Since several species of 

 Porcellanasfer have been named from very immature types, it is 

 probable that the adults will be difficult to identify correctly. 



Type.— Cat No. 28655, U.S.N.M. 



Type-locality.— Station 5513, Iligan Bay, northern Mindanao, lat. 

 8° 16' 45'' N.; long. 124° 02' 48" E.; 505 fathoms, bottom temper- 

 ature 52.8° F., gray mud and fine sand. 



Distribution.— Mindanao Sea and Sulu Sea, Philippine Islands. 



Specimens examined. — The type, and three immature from sta- 

 tion 5425, Sulu Sea, near Cagayanes Islands, 495 fathoms, gray mud, 

 coral sand, bottom temperature 49.4° F. 



Remarks. — As indicated in the diagnosis, the genus Benthogenia 

 is distinguished by the possession of an indefinite number of cribri- 

 form organs, these being present between all the marginals, by the 

 fusing of the cribriform organs of the interbrachium, by the presence 

 of a curious dorsal cribriform organ on the surface of those supero- 

 marginals which unite in the median line of ray, and by an entirely 

 dorsal spiniferous prominent terminal plale. The genus probably 

 stands nearest Hyphalaster.^ although resembling Thoracaster in the 

 abundance of artinal intermediate spinelets. The structure of the 



