32(i PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
investigations which show that the size of a star-fish is no criterion 
of its age, it becomes an interesting question whether the number 
of rays in this (and allied) species is dependent on the age of the 
individual, so that the older specimens have the fewer rays. The 
life history of this species would prove of exceptional interest, and 
it is to be hoped it will be worked out before long. 
Pteraster multispinus sp. nov. Plate 3, figs. 1 and 2. 
Rays 5. R : r: : 27 mm. : 18. R= 1J r. Breadth of ray at base 17 mm. 
Interbracliial arcs rather shallow. Disc almost flat, 10 mm. high, the rays not 
clearly marked off. Abactinal surface of rays almost flat; actinal surface flat, 
edges rounded. Supradorsal membrane thick, stout and apparently muscular, 
with no sign of reticulations. Spiracula seem to be absent on disc, but abun¬ 
dant near tips of rays. Paxillae high with numerous spines (8-10 or more), 
those in the middle little more slender than those on edge of paxilla. On account 
of the abundance of paxillae spines, it is almost impossible to determine whether 
the membrane contains any other calcareous bodies or not, but there seem to be 
none. Oscular orifice large, surrounded by long spines imbedded in the mem¬ 
brane. Ambulacral furrows broad ; feet in 2 rows. Adambulacral plates with 
6 spines, arranged in a row at right angles to furrow and united by a delicate 
membrane. The outermost spine is clearly united to the fifth by this mem¬ 
brane, and each series of spines is united by this membrane to the edge of the 
supra-dorsal membrane. Between each pair of outermost spines is a small sharp 
spine, the aperture papilla, which is nearly free on both sides. Mouth plates 
prominent, each with 3 marginal spines united by a delicate membrane, and 
with a very large, free, superficial spine, placed near the base, and pointing 
downward and backward. Color, in alcohol, grayish pink-purple. 
The single specimen of this interesting form bears no other label 
than the date “ 1897.” Unfortunately there is no clue as to the 
exact locality or the depth at which it was collected. It is some¬ 
what damaged, but seems to be very distinct from any species of 
the genus hitherto described. The only other Pteraster known 
from the North Pacific is P. aporus Ludw., collected in Behring 
Sea, which is characterized by the absence of an oscular orifice, so 
obvious in the present species. The name given has been selected 
on account of the large number of spines on each paxilla. 
Retaster gracilis sp. nov. Plate 3, figs. 3 and 4. . 
Rays 5. R: r : : 10:8, or 18:9. R=2 r. Breadth of arm at base equals r. 
Interbracliial arcs deep. Disc depressed, 0-8 mm. high, the rays not clearly 
marked off. Abactinal surface of rays rather arched; actinal surface flat, but 
edges rounded. Supradorsal membrane very thin and delicate; the tips of the 
spines from the edges of the paxillae connected by delicate lines giving the 
