NEW MARINE ISOPODS^ — MENZIES 119 



Family ASTACILLIDAE 



Only one species of this family, Astacilla calif omica Boone (1918, 

 pp. 600-601, pi. 89, fig. 1), has been previously reported from Cali- 

 fornia. Boone's species was collected at Venice, Calif., and is based 

 on a single adult female. The new species described herein was col- 

 lected by Joel W. Hedgpeth, and it is with considerable pleasure that 

 I name it after a man who has contributed so much to the study of 

 marine science in America. The species appears to be rare, at least 

 intertidally, in that a prior year of collecting failed to yield a single 

 specimen. As far as I know this is the first record of an Idarcturus 

 sj)ecies from the Northern Hemisphere. 



Genus IDARCTURUS Barnard, 1914 



IDARCTURUS HEDGPETHI, new species 



Figures 17, 18 



Holotype. — Ovigerous female, length 1.4 mm., width at widest part 

 of second peraeon somite 0.9 mm. 



Diagnosis. — Eyes lateral and bulging. Cephalon with two large 

 spines on dorsum above eyes. First peraeon somite fused with 

 cephalon, line of fusion indicated dorsally by a shallow tranverse 

 groove. Peraeon somites 1 to 7 with large triangulate anterolateral 

 extensions, those of somites 6 and 7 appearing more lateral than 

 anterolateral; somites 4 to 6 with large acute posterolateral spines; 

 dorsal surface of posterior areas of somites 2 to 7 with a trans- 

 verse row of four huge spines. Pleotelson composed of a single 

 somite ; each lateral margin with two large, angulate spines ; posterior 

 margin produced, apex blunt; dorsal surface near anterior end with 

 two large, dorsally directed spines. Spinelike epimeral plates present 

 on somites 3 and 4, those of somite 4 visible in dorsal view. 

 Palp of second antenna with a 3-jointed flagellum, last joint with a 

 large terminal claw. Maxilliped with two coupling hooks ; palp with 

 five segments. First peraeopod concealed from lateral view by lateral 

 extensions of cephalon and first peraeon somite; claw lacking on distal 

 joint. 



Character of hody. — Animal elongate, cream colored, body with 

 huge spines, eyes black. 



Ce/phalon. — Eyes bulging laterally. Anterior border deeply con- 

 cave, with a minute median projection. Dorsal surface above eyes 

 with two large laterally compressed spines. Lateral extensions of 

 united cephalon and first peraeon somite conceal mouth parts and first 

 peraeopod from lateral view. 



Peraeon. — First somite fused with cephalon, line of fusion indi- 

 cated dorsally by a shallow transverse groove, each anterolateral 



