2 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
typology in taxonomic accounts of pelagic invertebrates (cf. Simpson, 
1961, pp. 45-50); and (7) paucity or absence of a fossil record for 
most taxa. 
Many of these obstacles can be lessened materially by concentrating ; 
upon predominantly neritic taxa. Among the planktonic copepods; 
there are a number of large, essentially neritic genera from which to) 
select. One of these, the genus Labidocera (family Pontellidae), | 
offers several notable advantages for examining ecological, distribu- ‘| 
tional, and morphological relationships between closely related con-- 
geners. Species are relatively large in size and can be collected ini 
abundance. Sexually modified anatomical features are species-- 
specific and remarkably well developed. 
Ranges, which are limited to warm-temperate to tropical latitudes, | 
are sharply defined and tend to coincide with major zoogeographic as; 
well as inshore-offshore boundaries (Fleminger 1957, 1959; Heinrich, , 
1960; Voronina, 1962, 1964; Sherman, 1963, 1964). Range limits) 
conforming to oceanic barriers on the one hand and latitudinal | 
zonation on the other are relatively simple to determine and monitor? 
for an extended period of time. This lattermost feature confers: 
added advantages to the study of neritic Labidocera in the Western 
Hemisphere, where several distinctive species groups are found.. 
These species groups are adapted to coastal waters. Within a group, . 
the distribution and taxonomic relationships of its species constitute) 
a series of succeeding ranges like successive links in a chain. Taxo- 
nomic, morphological, and distributional relationships within and! 
between species groups of Labidocera found in the Western Hemisphere * 
are under study, one objective being to disclose patterns of evolu-- 
tionary consequence operating interspecifically on planktonic copepods, | 
Seven species of Labidocera are known to occur on the Pacific Coast: 
of the Americas (Giesbrecht, 1892; Esterly, 1905, 1906; Johnson, | 
1935; Wilson, 1942, 1950; Sherman, 1963; Fleminger, 1964a).? Of 
these, L. acutifrons and L. detruncata are typically oceanic, whereas 
L. acuta is more closely associated with continental and insular land ! 
masses. Three, L. trispinosa, L. johnson, and L. jollae, have been) 
found chiefly in inshore waters off California and northern Mexico / 
while the remaining species, L. lubbockii, is known only from the type’ 
locality, Golfo de Guayaquil, Ecuador. In the present study wo. 
additional species have been found. 
The two new species are closely related to LZ. jollae, and the three 
together comprise the subject of this paper. One of the new species | 
is especially noteworthy in that it is conspicuously dimorphic in the: 
i 
2Some of the records of Labidocera published by Wilson (1950) have been | 
omitted for reasons discussed elsewhere (Fleminger, 1965). | 
