NO. 1 BARNARD : AMPHIPODA OF THE FAMILY AM PELISCIDAE 5 



articles 3 and 4; the posterior lobe of article 4, its size and shape; the 

 shape of article 5 (the presence or absence of anterior notches and its 

 length relative to articles 4 and 6) ; and the length of article 6. 



7. Shape of the rami of uropod 3. These are of particular importance 

 in such species as Ampelisca pacifica Holmes and A. lobata Holmes, 

 where one of the rami is greatly modified. 



Of secondary importance in the genus Ampelisca are the following 

 characters : 



1. Length of article 7 of peraeopod 2. 



2. Shape and armature of telson lobes. 



3. Shape of article 6 of gnathopod 1. In some species, the posterior 

 edge of this article is strongly inflated, forming a false palm which is 

 usually strongly armed with spines and setae. Article 7 also may be 

 enlarged. 



4. Presence or absence of anterodistal process on article 5 of peraeo- 

 pods 3 and 4 (see Ampelisca milleri, new species). 



5. Presence or absence of a long spine at apex of outer ramus of 

 uropod 2. 



6. Lateral or medial ridges of dorsal surface of pleon segment 2 

 (also a secondary sexual character). 



7. Size of dorsal processes of pleon segment 6 (also a secondary 

 sexual character). 



8. Relative lengths of antennae and their segments to each other and 

 to the body length. Due to their fragility, a great many specimens of 

 Ampelisca reach the laboratory with the flagella or entire antennae 

 missing. 



Secondary Sexual Characteristics of the Genus Ampelisca 



In general, the adult male of a species of Ampelisca is rarely en- 

 countered. In exceptional cases an entire lot of material may contain 

 only males. Sexual dimorphism is usually limited to the following char- 

 acters found in the male: 



1. A row of setal tufts on the inferior edge of the peduncle of an- 

 tenna 1 and the superior edge of the peduncle of antenna 2 in the adult 

 male. 



2. The antennae may be longer than in the female. 



3. The dorsal process of pleon segment 4 may be more strongly 

 produced. 



4. The lateral processes of pleon segment 6 are more strongly de- 

 veloped. 



