AGASSIZ: PRELIMINARY REPORT ON THE ECHINI. 79 
tremity does not pass, as in E. cuneata, into the anterior ambulacral groove. 
The actinal system is protected by five large plates. 
Station No. 3398, off Galera Point, in 1573 fathoms. 
de “3399, off Galera Point, in 1740 fathoms, 
bie “ 3415, off Acapulco, in 1879 fathoms. 
Urechinus giganteus A. Ao. 
Plate VIII. Figs. 7, 8. 
At Station No. 3431 two specimens of Urechinus were collected, much larger 
than those of any of the species dredged by the “ Challenger” or the “ Blake,” 
the largest specimen measuring 93 mm, in length, 80 mm. in width, and 39 mm. 
in height. This species is also remarkable for the great length of the primary 
spines, which in proportion to the length of the test are nearly as long as those 
of Linopneustes, Above the ambitus the test is covered by minute miliaries, scat- 
tered uniformly over the surface of the coronal plates. The primary tubercles 
are placed uniformly over the abactinal part of the test both in the ambulacral 
and interambulacral areas. They are somewhat more closely placed near the 
ambitus and in the interambulacral areas of the actinal surface they are closely 
packed, forming a distinct actinal plastron in the odd interambulacrum. 
The phyllodes extend to the sixth or seventh pore from the actinostome. It is 
interesting to note that there are quite well developed “ bourrelets ” separating 
the ambulacral areas, a feature characteristic of such genera as Conolampas, 
Conoclypus, Echinolampas, and the like. 
Station No. 3431, off Altata, Gulf of California, in 995 fathoms. 
Cystechinus Loveni A. Ac. 
Plate IX. 
The test of this species is comparatively stout; it is closely allied to Cyste- 
chinus Wyvillii, but can at once be distinguished from it by its transverse anal 
system (it is longitudinal both im O. Wyvillii and ©. elypeatus), by the great 
size of the actinal interambulacral plate of the actinal plastron, and by the struc- 
ture of the apical system which is intermediate between that of O. clypeatus 
and ©. Wyvillii (Challenger Echini, Plate XXIX.” Fig. 1, and Plate XX XV.» 
Fig. 10). 
Station No. 3415, off Acapulco, in 1879 fathoms. 
Cystechinus Rathbuni A. Aa. 
Plate X. 
A number of specimens in excellent condition were dredged from the two 
localities at which this species was procured. The test of this species is thinner 
than in ©. Loveni, but somewhat thicker than in ©. vesica. A few of the speci- 
mens came up which had preserved their shape, so we are able to give figures 
