400 
PACIFIC SCIENCE, Vol. XIX, October 1965 
ble for study from the Scripps 1950-53 col- 
lections. 
In all eight species of Gnathophausia are 
recognized: G. ingens (Dohrn), G. gigas Wil- 
lemoes-Suhm, G. gracilis W-Suhm, G. zoea W- 
Suhm, G. elegans G. O. Sars, G. longispina G. O. 
Sars, G. affinis G. O. Sars, and G. scapularis Ort- 
mann. Of these eight species, four have been 
identified in the midwater trawl hauls from 
the Scripps 1950-53 collections in the eastern 
Pacific. They are G. ingens, G. gigas, G. gra- 
cilis, and G. zoea. 
SYSTEMATIC REVIEW AND MORPHOLOGY 
Since the time of Boas’ early report (1883) 
the mysidaceans have been separated from the 
euphausiaceans into two distinct orders of the 
crustacean subclass Malacostraca. These two 
groups had previously been joined in the order 
Schizopoda ( now abandoned ) of Latreille 
(1817). Hansen (1893) and Caiman (1904) 
further agreed with Boas in separating the two 
groups, allying the Euphausiacea with the Dec- 
apoda in the tribe Eucarida and allying the 
Mysidacea with the orders Cumacea, Tanaida- 
cea, Isopoda, and Amphipoda in the division 
Peracarida. An excellent review of the histori- 
cal systematics and nomenclature of the Mysi- 
dacea in relation to other crustacean groups 
appears in Tattersall and Tattersall (1951), 
and the reader is referred to this work for the 
detailed and complete summary. 
KEY TO SUBORDERS OF MYSIDACEA 2 
1. Branchiae ( podobranchiae ) present on some 
or all of the thoracic limbs. Marsupium of 
seven pairs of brood lamellae. Pleopods in 
both sexes with both rami multiarticulate 
and natatory; none secondarily modified in 
the male. No statocyst on endopod of uro- 
pod LOPHOGASTRIDA 
2. Branchiae (podobranchiae) absent. Marsu- 
pium generally of fewer than seven pairs of 
brood lamellae. Pleopods of male natatory or 
reduced, one or more pairs usually modified 
as accessory copulatory organs; pleopods of 
female reduced to simple undivided plates, 
not natatory. Statocyst usually present on 
endopod of uropod. ...... MYSIDA 
The suborder Lophogastrida, with which we 
are concerned in the study of Gnathophausia, 
is divided into two families: (1) the Lopho- 
gastridae containing five genera, Lophogaster, 
Paralophogaster, Chalaraspidum , Ceratolepis, and 
Gnathophausia; and (2) the Eucopiidae with 
the single genus Eucopia . 
2 From Tattersall and Tattersall, 1951. 
