A nth essius — I L LG 
351 
spicuous basal constriction. Medial row of 
spinules more extensive, reaching apex. 
Sixth legs (Fig. 23) ventrolateral on genital 
segment, involved in very complicated manner 
with structure of reproductive opening. Most 
obviously representative of appendage a small 
prominence bearing 2 setae, the more medial 
about half as long as lateral. 
REMARKS: The species seems to belong to a 
southern California fauna, as it was collected 
from at least two localities, Anaheim Slough and 
Laguna Beach, by the MacGinities. In consid- 
erable exploration and study of marine zoology 
on the West Coast no collections from further 
north have yet come to my attention, although 
the host is recorded as ranging very widely on 
the coast of California and has been closely ob- 
served frequently. Details of the antennules 
should be reinvestigated on freshly collected 
specimens. 
Anthessius lighti, new species 
Figs. 27-58 
TYPES: Holotypic female, USNM 103307, al- 
lotypic male, USNM 103308, paratypes, USNM 
103309; additional paratypes in Alan Hancock 
Foundation, University of Southern California, 
and in author’s collection. Type locality, Bodega 
Bay, California, from Aplysia calif ornica Cooper. 
SPECIMENS EXAMINED: Several lots of this 
species are included in the material studied, but 
as far as can be determined they represent 
a single collection from A. calif ornica, from 
Bodega Bay, California, June 1, 1941, O. Hart- 
man and E. C. Dougherty, many specimens, 
males and females. The descriptions below and 
the illustrations are based on a number of speci- 
mens, some unmounted, some whole mounts, 
some temporarily mounted dissections, some 
permanently mounted dissections. Two of the 
latter have been selected as holotype and allo- 
type. 
DESCRIPTION: Female (Figs. 27-43): Body 
length 2.67 mm., greatest width 1.14 mm., aver- 
ages for 10 specimens. Body (Figs. 27, 28) of 
rather generalized cyclopoid contours, but with 
most thoracic and abdominal segments distinct, 
so that regionalization is not emphatic. Cephalo- 
some a complex bearing appendages through 
first swimming legs and comprising .33 of total 
body length measured from apex of cephalosome 
to end of a caudal ramus. General contour and 
internal structure strongly indicating segment 
of leg 1 a part of cephalosome, but this seg- 
ment clearly demarcated dorsally and anteri- 
orly by continuous articulationlike groove and 
well-developed marginal indentations. Ventrally 
segment of leg 1 apparently contributing to 
cephalosome in forming massive midventral 
bulge between mouthparts and leg 1. First legs 
situated on posterior edge of segment, directed 
posteriorly, obviously behaving functionally as 
part of metasomal group of legs. On anterior 
margin apex of head protruded in a slight bulge 
between bases of widely separated antennules. 
No rostrum, apical ventral region of head a wide 
flattened expanse between bases of antennules 
and antennae. Metasome including pedigerous 
segments of second through fourth legs, with 
general body articulation between segments of 
legs 4 and 5. Segment of fourth legs with dis- 
tinctive bilateral, ventral structures. Fourth legs 
borne on anterior end of ventral surface of seg- 
ment. At each side on posterior region of ventral 
surface two subequal lobes extending posteriorly. 
Lobes visible in dorsal view (Fig. 30) of intact 
animal, as lying between segments of legs 4 and 
5 and medial to the fourth legs. Urosome a com- 
plex including segment of legs 5, a genital seg- 
ment and 3 additional abdominal segments, con- 
sidering element bearing anus and supporting 
caudal rami as terminal segment. Segment of 
fifth leg, as in other pedigerous segments, with 
dorsal epimeralike lateral expansions. Urosome 
comprising .45 of total body length. Genital 
segment expanded laterally, dorsally with dis- 
FlGS. 27—39: Anthessius lighti, new species. The scales accompanying certain figures represent 0.1 mm. 
Female: 27, habit, dorsal; 28, habit, lateral; 29, egg sack; 30, lateral part of segment of fourth leg and ad- 
joining structures, dorsal view; 31, antennule; 32, antenna; 33, oral area; 34, mandible; 35, maxillule; 36, 
maxilla; 37, maxilliped; 38, fifth leg and lateral portion of genital segment; 39, caudal ramus. Legend: B, 
base of fourth leg; E, epimeron of segment of fourth leg; L, labrum; M, mandible; P, maxilliped; R, pro- 
tuberance of unknown significance at base of fourth leg; U, maxillule; V, segment of fifth leg; X, maxilla. 
