MARINE ISOPODA OF NEW ENGLAND, ETC. 309 



Actoniscus Harger. 



Actoniseus Harger, Am. Jour. Sci., Ill, vol. xv, p. 373, 1878. 



Eyes small ; anteuupe geniculate at the third and fifth segments ; fla- 



gellum four-jointed ; terminal segments of maxillipeds lamelliform, lobed; 



legs all alike; basal segment of uropods dilated and simulating the 



coxte of the preceding segments of the pleon ; rami both styliform. 



This genus resembles Actwcia Dana* MSS., considered as the young of 

 8cyphax ornatufi, and found with it on the beach at New Zealand. Pro- 

 fessor Kinahan,t on the other hand, regarded the genus as indicating a 

 distinct family. The present genus diifers from the description and 

 figures of Professor Dana as follows : The flagellum of the antennse con- 

 sists of only foui' distinct segments instead of about six ; the terminal 

 segment of the maxillipeds is less distinctly lobed ; the inner ramus of 

 the uropods surpasses the outer, instead of falling far short of it ; the 

 outer ramus is styliform instead of being enlarged and subequal to 

 the produced and enlarged outer angle of the basal segment. 



Actoniscus ellipticus Harger. 



Actoniscus elUpticm Harger, Am. Jour. Sci., Ill, vol. xv, p. 373, 1878; Proc. 

 U. S. Nat. Mus., 1879, vol. ii, p. 157, 1879. 



Plate I, Fig. 3. 



This species may be at once recognized by the pleon, which appears 

 to have four pairs of coxai produced at the sides instead of three, as in 

 Oniscus and other genera of this family. The last pan- are, however, 

 the basal segments of the caudal stylets, which are of peculiar form in 

 this genus. 



The body is oval in outline. The head appears triangular as seen from 

 above, and is angularly produced in a median lobe, but the lateral lobes 

 are also large and divergent, and broadly rounded. The eyes are small, 

 oval, black, and prominent. They are situated at the sides of the me- 

 dian triangular part of the head, and at the base of the lateral lobes. 

 The antennulse are minute and rudimentary. The antennae have the 

 basal segment short; the second enlarged distally, especially on the 

 inner side; the third forming an angle with the second, and clavate; 

 the fourth' flattened-cylindrical, longer than the third; fifth longest, 

 slender, bent at base and forming an angle with the fourth; fiagellum 

 shorter than the last peduncular segment, tipped with setae and com- 

 posed of four segments, of which the second and third are equal and 

 longer than the first, while the last is the shortest, and presents indica- 

 tions of another minute rudimentary terminal segment. The maxil- 

 lipeds have the basal segment nearly twice as long as broad; the 

 terminal segment elongate triangular, ciliated and somewhat lobed near 

 the tip. 



*U. S. Expl. Exped. Crust., part ii, p. 736, pi. 48, fig. 6 a-h. 

 t Natural History Review, vol. iv, Proc. Soc., p. 274, 1857. 



