Mysidacea and Euphausiacea — BANNER 
131 
on the closely related N. rayi (Murdock) this 
was shown to be an unreliable characteristic. 
Probably the most firm of the criteria might 
be found in the shape of the rostral plate and 
the fourth pleopods of the male. However, it 
was precisely these characteristics again that 
were found to be without worth in the at- 
tempted separation of N. rayi from N. fran- 
ciscorum. In fact, the differences in this com- 
plex parallel the differences found between 
the warm-water N. franciscorum (as it was pre- 
viously known) and the colder-water N. rayi. 
Unfortunately, the collections do not per- 
mit the complete removal of all differences, 
but when it is considered that there are 
stretches of the coast of the North Pacific 
hundreds of miles long where the species 
must exist but where no collections have ever 
been made, it is logical to presume that com- 
plete intergradations between the various 
types could be found. 
It is for these reasons that N. mercedis and 
N. intermedia have been placed in synonymy 
to N. awatschensis. 
Acanthomysis pseudomacropsis 
(Tattersall) 
Neomysis pseudomacropsis Tattersall, Contrib. 
Canad. Biol. 8: 94-97, figs. 7a-b, 8a-f, 
1933. 
Acanthomysis pseudomacropsis Banner, Roy. 
Canad. Inst., Trans. 27: 89, 1948. 
Tattersall, U. S. Natl. Mus., 
Bui. 200: 217, figs. 91, 92, 1951. 
SPECIMENS examined: King Crab Investiga- 
tion: No. C-109, stomachs of Gadus macro- 
cephalus, Point Moller, Alaska, May 6, 1941. 
Two specimens from separate stomachs. 
No. C-117, stomach of Theragra chalco- 
gramma, Cape Seniavin, Alaska, May 8, 1941. 
Twenty specimens. 
DISCUSSION: Previous records of this species 
have extended from Washington to the coast 
of Siberia; these records, therefore, do not 
extend the range. 
Acanthomysis sculpta (Tattersall) 
Neomysis sculpta Tattersall, Contrib. Canad. 
Biol. 8: 197-200, figs. 9a-b, lOa-d, lla-b, 
1933. 
Acanthomysis sculpta Banner, Roy. Canad. Inst., 
Trans. 27: 97-99, 1948. 
Tattersall, U. S. Natl. Mus., 
BuL 201: 248, 1951. 
SPECIMENS EXAMINED: Fifteen specimens 
from Pismo Beach, California (about 50 miles 
north of Point Conception), from the sand 
in the intertidal zone, Nov., 1946; A. H. 
Banner, collector. 
DISCUSSION: As this species is known from 
Vancouver Island, Canada, to La Jolla, Cali- 
fornia, this record merely fills in part of the 
range. 
Acanthomysis alaskensis n. sp. 
Fig. 2 
DESCRIPTION: Rostrum triangular, acute, 
with tip reaching almost to the proximal por- 
tion of cornea of eye; dorsal surface straight 
in profile. Anterolateral corners of carapace 
produced and acute. 
Eyes large, with peduncle short and heavy, 
broader than long. Inner superior surface of 
peduncle with poorly developed triangular 
papilla. Cornea expanded, dorsoventrally com- 
pressed and subovate in lateral view. 
Antennular peduncle showing usual sexual 
dimorphism, in males with distal article heav- 
ier than in females and bearing well- developed 
process masculinus. Basicerite of antenna bear- 
ing a small but acute tooth. Antennal pedun- 
cle reaching only to middle of last article of 
antennular peduncle. Squame twice as long 
as antennular peduncle, six times as long as 
broad; distal twentieth demarked by feeble 
articulation. 
Labrum with acute anterior process. 
Protopodite of first thoracic leg laterally 
expanded so that exopod and endopod are 
some distance removed from each other, and 
bearing well- developed, lobe-like endite. Pro- 
podi of third to eighth thoracic legs with 6 
