364 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Astacilla granulata Harger (G. O. Sars). 



Leachia granulata G. O. Sars, Arch. Math. Nat., B. ii, p. 351 [251], 1877. 

 AstaciUa Americana Harger, Am. Jour. Sci., Ill, vol. xv, p. 374, 1878. 

 Astacilla granulata Harger, Proc. U. S. Nat. Mus., 1879, vol. ii, p, 161, 1879 



PLATES VIII AND IX, FIGS. 48-52. 



The elongated fourth thoracic segment distinguishes this species at 

 once from all the other Isopoda of our coast. 



The body is in the female eight times and in the male about twenty 

 times as long as broad, the breadth being measured across the fourth 

 thoracic segment. It is roughened and tuberculated throughout. The 

 head is produced at the sides in front beyond the middle of the basal 

 segment of the antennula3, and is tuberculated above and crossed by 

 two transverse grooves, the first between, and the second behind the eyes, 

 while a third similar groove evidently marks the place of the suture be- 

 tween the head and the first thoracic segment. The eyes are lateral, 

 prominent, round-ovate, broadest in front. The antenuulae in the female 

 slightly surpass the second segment of the antenna, in the male they nearly 

 attain the middle of the third segment, the flagellar segment being 

 elongated in the male, longer than the three peduncular segments 

 together (pi. VIII, fig. 48 a). The second and third segments of the 

 antenuulae are in both sexes short and slender. The antennae are fully 

 three-fourths as long as the body ; the first segment is shorter than that 

 of the autenuulae, being surpassed at the sides by the lateral processes of 

 the head and thus concealed in a lateral view ; the second segment is 

 large, scarcely longer than broad, and presents below a deep angular 

 sinus in the distal margin, as in Idotea ; third segment about as long as 

 the head; fourth segment longest, slightly exceeding the fifth, which is 

 equal to the first three taken together. The flagellum* (pi. VIII, fig. 49 a) 

 is less than half the length of the last peduncular segment and usually 

 consists of three distinct segments, of which the first is as long as the 

 other two ; the second is equal in length to the third, which is tipped 

 with a terminal spine or claw, probably to be regarded as a fourth seg- 

 ment. Sometimes, however, only two distinct segments exist in the 

 flagellum besides the claw. The flagellar segments are finely and 

 sharply denticulate along the margin which is inferior when the an- 

 tennae are straightened. The character of this deuticulatiou is shown 

 in figure 49 a' on plate VIII, where a small section of the margin is shown 

 enlarged 100 diameters. The maxillipeds (pi. IX, fig. 52 a) are robust 

 and cover the other parts of the mouth; the external lamella (I) is 

 ovate and in the figure is somewhat bent outward from its natural 

 position. The palpus of the maxillipeds is five-jointed and but little 

 flattened, strongly ciliated along the inner margin. The terminal lobe 



* The figure of the animal (pi. VIII, fig. 48,) was sent to the engraver hefore I had 

 Been any specimens except the imperfect ones collected in 1877, and the flagellum of 

 the antenna was dotted from the young specimens. Fig. 49 a on plate VIII was 

 made from a specimen obtained in 1878. 



