284 BULLETIN 15, tTNTTED STATES NATIONAL MUSEUM. 



ASTROCERAS PERGAMENA. 



Aslroceras pergamena Lyman, Bull. Miis. Comp. Zool., vol. 6, 1879, p. 62. 



Localities. — Albatross station 3716, off Ose Zaki, Honshu Island, 

 Japan, 65 to 125 fathoms, volcanic sand, shells, rocks, 17 specimens; 

 station 3729, off Omai Zaki, Honshu Island, Japan, 34 fathoms, mud, 

 gravel, 1 specimen; station 3730, off Omai Zaki, Honshu Island, 

 Japan, 34 to 37 fathoms, mud, gravel, rocks, 5 specimens; station 

 3735, off Omai Zaki, Honshu Island, Japan, 36 fathoms, coarse gray 

 volcanic sand, broken shells, 33 specimens; station 3755, off Suno 

 Saki, Honshu Island, Japan, 52 to 77 fathoms, gray sand, coral, 4 

 specimens; 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°, 3 specimens; station 4894, Eastern Sea, lat. 32° 

 33' N.; long. 128° 32' 10" E., 95 fathoms, gray sand, broken shells, 

 pebbles, 2 specimens; station 4895, Eastern Sea, lat. 32° 33' 10" N.; 

 long. 128° 32' 10" E., 95 fathoms, gray sand, broken shells, pebbles, 



1 specimen; station 4936, Eastern Sea, lat. 30° 54' 40" N.; long. 130° 

 37' 30" E., 103 fathoms, stones, bottom temperature 60.6°, 1 speci- 

 men; station 5070,Suruga Gulf, lat. 35° 3' 25" N.; long. 138° 47' 40" 

 E., 108 fathoms, mud, sand, broken shells, bottom temperature 57.6°, 



2 specimens. Bathymetrical range, 34 to 125 fathoms. Tempera- 

 ture range, 60.6° to 55.9°. Sixty-nine specimens. 



This is a remarkably interesting series of specimens ranging in 

 disk diameter from 1 to 8 mm. The smallest specimens have no 

 tubercles on either radial sliields or arms, but these appear most 

 irregularly with increasing size, those on the radial shields appearing 

 first, but some of those on the basal joints of the arm may appear 

 before all the radial shields have them; thus in a specimen 5 mm. 

 across the disk there are tubercles on the basal joints of all the arms 

 but only on four of the radial shields. Another specimen 5 mm. 

 across has each of the radial shields provided with a tubercle, as in 

 Lyman's type, and similar ones are present on the two basal joints of 

 each arm. In the specimens 8 mm. across the disk, the tubercles are 

 present but not equally developed, on the basal six or seven joints of 

 each arm. On the disk and arms of the smallest specimens are 

 minute, round, calcareous granules, and on the arms these are arranged 

 in very regular transverse rows, corresponding to the upper arm 

 plates. As growth goes on and the large tubercles appear these 

 granules disappear, first from the disk and then from the base of the 

 arm, but even in the largest specimen they are abundant beyond the 

 basal part of the arm. Lyman does not refer to their presence in the 

 type-specimen, wliich was 19 mm. across the disk, so that it is prob- 

 able they ultimately all disappear. 



Another most interesting fact revealed by the series before me is 

 that the young Astroceras has, like many specimens of Amphiuridse, 



