36 University of California Publications in Zoology [Vol. 23 



Characters. — Bostrum longer than carapace, and tapering more or less evenly 

 from the widest portion (which is about one-fourth as wide as the rostrum is long) 

 to an acute tip; armed above with seven to eight teeth, one or two of which 

 are behind the orbit; below with three teeth. Ocular peduncles short and stout; 

 the ocellus lies between the cornea and the stalk. Antennal scale is shorter than 

 the rostrum, with blade exceeding the spine. 



Dimensions. — Type: length 45 mm. 



Type Locality. — San Diego, California. 



Distribution. — From San Diego, California, to Gulf of California (Eathbun). 

 Bay of St. Elena, Ecuador (Nobili). 



Genus Palaemonetes Heller 



Bostrum prominently toothed above and below. Carapace furnished with 

 antennal and branchiostegal spine, but without hepatic spine. Mandible without 

 palp. 



Palaemonetes hiltoni sp. nov. 



Plate 12, figure 5 



Description. — Closely allied to P. kadiakensis Bathbun (1902, p. 903; 1904a, 

 p. 30, fig. 9), from Alaska, and intermediate between it and P. vulgaris Say 

 (1818, p. 248), of the Atlantic. 



It differs from both P. kadiakensis and P. vulgaris in the proportional length 

 of the propodal and carpal joints of the first two pairs of legs and in the relative 

 length of the sixth abdominal segment as compared to the fifth. The following 

 table will suffice to show these differences in the three species mentioned above : 



Palaemonetes kadiakensis P. hiltoni P. vulgaris 



First pair of legs, 



propodus : carpus 1 : 2.20 1 : 1.75 1 : 1.50 



Second pair of legs, 



propodus : carpus 1 : 2.00 1 : 1.00 1 : 0.60 



merus : carpus 1 : 1.50 1 : 1.00 1 : 0.88 



Abdomen, fifth segment : sixth 1 : 2.00 1 : 1.66 1 : 1.50 



Otherwise the description and figure of P. kadiakensis as given by Miss Bath- 

 bun does very well for P. hiltoni. On the whole P. hiltoni is the stouter of the two 

 with less elongate and attenuate legs and a relatively shorter and stouter sixth 

 abdominal segment. 



Begarding the number of rostral teeth of P. hiltoni, as only four specimens have 

 been seen, no positive statement can be made. Those examined all had nine teeth 

 on the rostrum and an additional one on the carapace behind the orbit; beneath 

 the number ranged from three in three of the specimens to four in the fourth one. 

 In P. kadiakensis the count based on a large number of specimens ranges from 

 six to ten teeth above, of which one or two are behind the orbit, and from two to 

 three teeth below. 



Dimensions. — Holotype (Cat. No. 48991, U. S. N. M.): length from tip of 

 rostrum to end of telson 26 mm. ; carapace and rostrum together 10.5 mm. The 

 three paratypes are respectively 20, 21, and 24 mm. in length. 



Type Locality. — San Pedro, California (Stout and Stafford coll.). 



