364 
PACIFIC SCIENCE, Vol. XIV, October I960 
usually readily detected if the host is held in sea 
water for observation. There has been no inter- 
action so far detected between the copepod and 
the other extremely commonly occurring asso- 
ciate of D. aspera, the polynoid worm Arctonoe 
vittata ( Grube ) . The large limpets of the genus 
Acmaea x living in the same environment as the 
host, sometimes will be found to have a speci- 
men of A. nortoni in the respiratory cavity, but 
I feel that present evidence does not justify 
considering this as a regularly occurring associa- 
tion. The typical host should be further explored 
for this associate over its considerable range; 
I suspect the copepod will be found to have a 
wide distribution. This is one of the very small 
species of Anthessius, and in many regards it 
shows resemblance to the common European 
A. arenicolus and A. teissieri . However, it is 
distinctive anatomically, as expressed in part in 
the key to species above. It is the first member 
of the genus so far reported in association with 
an aspidobranch gastropod. 
Anthessius fitchi, new species 
Figs. 92-125 
TYPES: Holotypic female, USNM 103301, al- 
lotypic male, USNM 103302, paratypes, USNM 
103303; paratypes in author’s collection. Type 
locality, Carpinteria, California, from Chaceia 
ovoidea (Gould). 
SPECIMENS EXAMINED: From C. ovoidea: 
Carpinteria, California, November 11, 1954, J. E. 
Fitch, many specimens, females, males, including 
holotype and allotype. 
Carpinteria, California, January 1, 1956, J. E. 
Fitch, 50 + specimens. 
From Zirfaea pilsbryi Lowe: Fossil Point, 
Coos Bay, Oregon, July 23, 1959, 1 $ . 
The description below and the illustrations 
are based on a number of specimens, some un- 
mounted, some whole mounts, some temporarily 
mounted dissections, some permanently mounted 
dissections. Holotype and allotype are perma- 
nently mounted dissections. 
DESCRIPTION: Female (Figs. 92-102, 104- 
110): Body length 5.8 mm. (5. 6-6.1), greatest- 
width 2.1 mm. (2. 0-2.3), based on 10 speci- 
mens. Body ( Fig. 92 ) of this gigantic species 
of most distinctive habitus, retaining only gen- 
eral overall cyclopoid contours. Salient charac- 
teristics of habitus consist in much expanded 
outline of cephalosome, elongate antennules, 
much expanded lateral winglike epimera of 
thoracic segments, lateral expansions of genital 
segment, elongate and distally widened anal 
segment, and elongate, flattened and widened 
caudal rami. Not continuously present on adults, 
but of such distinctive nature as to contrib- 
ute to definite aspect of characteristic habitus, 
elongate stringlike egg sacks and persistently 
attached stalked spermatophores. Cephalosome 
a fused complex bearing appendages through 
first swimming legs without any demarcation of 
segment of these latter. Cephalosome compris- 
ing .25 of total body length. Apically a slight 
protrusion between bases of antennules. Ven- 
trally, area between antennular bases somewhat 
bulged and outlined by cuticular thickenings, 
but not developed as a proper rostrum ( see Fig. 
117 for this feature in male). Metasome of 3 
pedigerous segments, each with widely flaring 
lateral winglike epimera, those of first meta- 
somal segment much the widest, those of next 2 
segments successively diminishing. Urosome a 
complex including segment of legs 5, genital 
segment and 3 additional abdominal segments, 
considering element bearing anal opening and 
caudal rami as terminal segment. Urosome com- 
prising .55 of total body length. Segment of 
fifth legs (Fig. 102) lacking epimera, but with 
lateral expansions of entire mass of segment. 
Anterior and posterior margins of segment of 
about same width, greatest lateral extent about 
2.33 times width of anterior margin. Each lateral 
protrusion also somewhat inflated, with resultant 
structures extending almost to center of seg- 
ment. Fifth legs inserted apically on each ex- 
pansion. Genital segment also of very distinctive 
outline, with two widely extending lateral ex- 
FlGS. 92—103: Anthessius fitchi, new species. The scales accompanying certain figures represent 0.1 mm. 
Female: 92, habit, dorsal; 93, antennule; 94, antenna; 95, oral area; 96, labrum and supporting structure of 
oral area with appendages removed; 97, mandible; 98, maxillule; 99, maxilla; 100, maxilliped; 101, apex of 
maxilliped; 102, segment of fifth legs, dorsal. Male: 103, habit, dorsal. Legend: L. labrum; M , mandible; P , 
maxilliped; U, maxillule; X. maxilla. 
