238 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



which they are separated are not of very great value, but I have never 

 been at a loss in recognizing them, even when there has been some 

 encroachment upon their distinctive features. Thus I have had oc- 

 casion above to record two specimens of 0. galatheae from Dumu- 

 rug Point in which the radial shields, instead of being entirely 

 naked, as is ordinarily the case, show on their surface a certain num- 

 ber of granules similar to those of the rest of the dorsal surface of 

 the disk; but these granules, which are few in number, do not form 

 a covering comparable to that which is found in O. longipeda, from 

 which O. galatheae is sharply distinguished by its arm spines. 



Moreover, the form of the first ventral arm spine when transformed 

 into a hook may furnish a good criterion for determination. In 0* 

 hirsuta it shows the characters which are usually met with in the 

 species of the genus Ophiothrix; it is large, with three or four points 

 only, the terminal point is very strong and strongly recurved, and 

 the following are smaller and diminish rapidly in size (pi. 99, fig. 

 2&). In O. galatheae, O. longipeda, and O. puncto-lirribata the first 

 ventral spine does not form a hook, properly speaking : it resembles 

 rather a spine furnished on its concave border with many successive^ 

 elongated, closely crowded points which are arranged parallel to each 

 other. However, it is especially in 0. longipeda (pi. 100, fig. 2d) 

 and 0. puncto-linibata (pi. 101, fig.. 75) that these characters are 

 shown with the greatest clearness; in O. galatheae the transformation 

 into a hook is more pronounced and the lateral points are less numer- 

 ous (pi. 99, fig. If) . In these three species once the definitive charac- 

 ters are acquired the first ventral spine always remains of relatively 

 small dimensions. 



Generally speaking, the examination of this spine permits the dif- 

 ferentiation of 0. galatheae, 0. hirsuta, and O. longipeda; as for O. 

 puncto-lirribata, it is evidently very close to 0. longipeda*; in my 

 opinion it is the -only form of the group about which it is possible 

 to have doubts regarding its specific validity. 



I have given above my views on the subject of 0. rhabdota, which 

 I consider as a variety of O. expedita. 



OPHIOTHMX FOVEOLATA Marktanner. 



Plate 47, figs. 4-7 ; plate 98, fig. 6. 

 See for bibliography: 



OpMothrix foveolata KOSHLER ('05), p. 76; ('10), p. 294. MACINTOSH 

 ('11), p. 161. H. L. CLARK ('15), p. 280. 



Locality. Albatross station 5131; Sulu (Jolo) Sea, off western 

 Mindanao; island off Panabutan Point bearing N. 20 E., 0.74 kilo- 

 meter (0.4 mile.) distant ; 49 meters (27 fathoms) : February 6, 1908 ; 

 gn. M., co. S. 



Two specimens (Cat. No. 41025, U.S.N.M.). 



