CLARK: PUGET SOUND ECHINODERMS. 
327 
abactinal surface a reticulated appearance. This is much more evident in the 
smaller specimen, the lines in the larger specimen being very indistinct. 
Spicules seem to be entirely wanting in the membrane. Spiracula quite numer¬ 
ous, 6 to 10 in each mesh of the reticulum. Paxillae high, with 0 or more 
(often many more) spines surrounding edge and several smaller ones erect in 
middle. Oscular orifice present, but not especially noticeable. Adambulacral 
plates with G spines arranged in a row at right angles to furrow. Of these the 
first is very small, the second larger, the third still larger, the fourth still larger, 
the fifth equals the third, while the sixth is largest of all. The first five are 
united by a delicate membrane, but the sixth is almost wholly free. The sixth 
spines of all of the adambulacral plates are united with each other by a mem¬ 
brane parallel to the ambulacral furrow, and this is apparently separate from 
the supra-dorsal membrane. Aperture papillae very small, and free only on 
one side. Mouth plates prominent, each with 2 spines on edge, united by a 
membrane, and a very large spine on oral surface near base, pointing downward 
and outward. This spine is free and not connected with anything else by a 
membrane. Ambulacral furrows broad ; feet comparatively few, in two rows. 
Color of whole star-fish, light brownish gray, darkest on disc, lightest near tip 
of rays. 
There are two small specimens of this graceful little star-fish, hut 
there is nothing to indicate where or when they were taken. The 
smaller of the two specimens seems to have the characters of 
Retaster fairly well marked, hut the larger is much more like 
Pteraster. Not being able, however, to find any spicules in the 
supradorsal membrane in either specimen, it seems best to put them 
in the former genus. No specimen of Petaster has hitherto been 
recorded from the North Pacific, nor indeed from any point nearer 
to Puget Sound than the northeast coast of Australia. The name 
gracilis has been chosen for this species on account of its very deli¬ 
cate structure and beauty of form. 
Cribrella laeviuscula Stimpson. 
There seem to be two well-marked varieties of this species, one 
with short, stout rays, the other with the rays long and slender. 
Dr. H. P. Johnson tells me that the two forms intergrade, but in 
the collection before me there are no intermediate specimens. 
There is only one specimen of the slender variety and in that one 
R = 5 r. In the 25 specimens of the other variety, R = 3J r or less. 
Dr. Johnson has suggested the names crassa and attenuata for 
these two forms. They may be characterized thus : 
C. laeviuscula crassa. Disc large ; rays short and stumpy, terete, 
thick at base. II — 2-3£ r. 
