NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 109 



OPHIOMUSIUM SIMPLEX. 



Ophiomusium simplex LYMAN, Bull. Mus. Comp. Zool., vol. 5, 1878, p. 115. 

 Ophiomusium sanctum KCEHLER, Siboga Oph. Mer Prof., 1904, p. 59. 



Localities. Albatross station 4888, Eastern Sea, lat. 32 26' N.; 

 long. 129 27' 30" E., 71 fathoms, dark gray sand, broken shells, 

 bottom temperature 59.7, 1 specimen; station 4893, Eastern Sea, 

 lat. 32 32' N.; long. 128 32' 50" E., 95 to 106 fathoms, gray sand, 

 broken shells, pebbles, bottom temperature 55.9, 2 specimens; 

 station 4894, Eastern Sea, lat. 32 33' N.; long. 128 32' 10" E., 95 

 fathoms, green sand, broken shells, pebbles, 2 specimens; station 

 4895, Eastern Sea, lat. 32 33' 10" N.; long. 128 32' 10" E., 95 

 fathoms, green sand, broken shells, pebbles, 1 specimen; station 

 4903, Eastern Sea,lat.32 31' 10" N. ; long. 128 33' 20" E., 107 to 139 

 fathoms, gray sand, broken shells, 7 specimens; station 4936, Eastern 

 Sea, lat. 30 54' 40" N.; long. 130 37' 30" E., 103 fathoms, stones, 

 bottom temperature 60.6, 3 specimens. Bathymetrical range, 71 to 

 139 fathoms. Temperature range, 60.6 to 55.9. Sixteen specimens. 



As these specimens range in size from 4 to 14 mm. across the disk, 

 they serve to connect Lyman's single specimen of simplex (disk 

 diameter, 6 mm.) with Koehler's specimens of sanctum (disk diam- 

 eter, 10 to 19 mm.). The specimen 4 mm. across is almost exactly 

 like Lyman's description and figures, while the largest specimen 

 answers too well to Koshler's to permit any doubt as to its identity. 

 It is clear, therefore, that in this species the growth changes involve 

 an increasing swelling of the disk plates, especially the marginal ones, 

 a wide separation of the radial shields, a greater or less separation 

 of the five primary radial plates, an increase in the number of disk 

 scales, the addition of two plates in the interbrachial space below, 

 and often, but not always, the addition of a third arm spine. On 

 the other hand, there is absolutely no change in the under arm plates 

 and tentacle pores, and practically none in the upper arm plates, 

 oral shields, and mouth parts. These facts are of importance in 

 determining the validity of species within the genus, and their rela- 

 tionship with each other. 



OPHIOMUSIUM TRYCHNUM, new species.a 



Disk 18 mm. in diameter; arms about 70 mm. long. Disk some- 

 what elevated, 6 mm. thick, covered with about one hundred and 

 fifty scales, of which the six primary plates, three large plates in 

 each interradius and three smaller ones in each radius, are most 

 conspicuous. Each of these is swollen into a large central tubercle, 

 or flattened, elevated area. Kadial shields large, much longer than 



a Tpu%vo, signifying rough, rugged, in reference to the lumpy disk scales. 



