Laguna C0anne Laboratory 117 



than antepenultimate and slightly shorter than last; last two joints 

 very heavy and armed with stout spines. Second antenna? with 

 fourth joint distinctly separated, the outer branch with terminal 

 claw longer than claw of inner branch. The tuft of spines on outer 

 margin of third joint of inner branch, nearer to apex than base. 

 Mandibles at masticatory margin broader than at insertion of pal- 

 pus; palpus with respiratory plate not distinctly separated, but its 

 three spines are large, recurved and heavily plumose; the terminal 

 portion of palpus distinctly one-jointed; one large spine at base of 

 palpus. Second leg with basal joint shorter than second, the fourth 

 but little longer than third. 



Subclass CLADOCERA 

 Chydorus simplex n. sp. 



(Figure 64) 



With Diaptomus stagiialis and Cyprinotus calif ornicus, Mr. Hall 

 took numbers of an exceedingly minute (length .4-.5 mm.) Chydorus. 

 The anterior projection of the shell is long, very slender, and very 

 sharp, and is frequently more closely incurved to the anterior margin 

 of the shell than in the specimen drawn. The shell has a depth about 

 three times the hind margin. The distal (lower) margin is edged 

 with minute short plumed hairs to a point in front of the legs where 

 the curve to the anterior angle begins, and from that point to the 

 anterior angle they are replaced by small teeth. The postabdomen 

 is long subrectaugular, the terminal claws shorter than its greatest 

 width and these claws provided with a rather strong lateral tooth 

 behind. Lower hind border of postabdomen with a number of small 

 tufts of short hairs which are longer distally. Two long spines occur 

 above the anal opening. Posterior intestinal coecum long and slender. 



