326 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



ASTACILLA Ci^CA Benedict. 



Astacilla cseca Benebict, Proc. Biol. Soc. Washington, XII, 1898, p. 51. — Richard- 

 son, American Naturalist, XXXIV, 1890, p. 230; Proc. U. S. Nat. Mas., 

 XXni, 1901, p. 550. 



Locality. —\j2it\t\x&e 38^ 22' north, longitude 70^ 17' 30" west (south 

 of Marthas Vine3^ard). 

 Dej)th.~l,8'-25 fathoms. 



Body narrow, elong-ate, live times longer than wide, 2 mm. : 9^ mm. 

 Head wider than long, 1 mm. : li mm., with the anterior margin 

 deeply excavate between the produced antero-lateral 

 angles, and a small median point w ithin the excavation. 

 The lateral margin on either side is produced in two 

 acute triangular processes, an anterior and a posterior 

 lobe. The e3"es are wanting. There are two tubercles 

 on the head situated in the median line, one on the 

 anterior portion and the other on the postcephalic 

 lobe. The first pair of antennae have the basal article 

 long and dilated; the second and third articles are sub- 

 ecpial in length, slender, and both together about equal 

 in length to the basal article; the fourth article is one 

 and a half times longer than the third. The first an- 

 tenna extend a little beyond the end of the second arti- 

 cle of the peduncle of the second pair of antennae. The 

 basal article of the second antennae is short and incon- 

 spicuous in a dorsal view, being covered by the basal 

 article of the first antenna^; the second article extends 

 as far as the middle of the fourth article of the first antennge; the third 

 article is twice as long as the second; the fourth is twice as long as the 

 third; the fifth is a little shorter than the fourth. The 

 flagellum is composed of five articles. The second an- 

 tennte are 6 mm. in length. 



The first three segments of the thorax are subequal in 

 length; the fourth segment is six times longer than the 

 third, being 3 mm. in length; the fifth, sixth, and sev- 

 enth segments decrease gradually in length, the fifth 

 segment being about 1 mm. long. There is one median 

 tubercle on each of the thoracic segments; other small 

 tubercles are situated in a transverse line lateral to the 

 median tubercle on the first three segments; the fourth 

 segment is thickly covered with small tubercles over the 

 whole dorsal surface; the fifth segment has a pair of 

 tubercles one above the other on either side of the lateral 

 margin anterior to the epimera; the sixth segment has one tubercle on 

 either side anterior to the epimera. The epimera of the second, third, 

 and fourth segments are small; those of the last three segments are 

 angular and conspicuous. The fourth segment of the thorax is twice 



Fig. 357.— Astacil- 

 LA CMC A (After 

 Benedict). 



Fig. 358.— Asta- 

 cilla c.eca. 

 maxili.iped. 

 X 39. 



