144 Messrs. T. and A. Scott on some 



wliile the outer brandies are only equal to two thirds the 

 length of the inner ones. It also differs in the proportional 

 lengths of the other thoracic feet, as shown by the description 

 and figures. 



AscomyzontidsB. 



Dcrmatomyzon gihherunt'^, sp. n. (PI. IX. figs. 10-14.) 



Length 'b millim (5^ of an inch) . Cephalothorax very 

 tumid, broadly obovate or pear-shaped, the forehead being 

 regularly and boldly rounded ; the first body-segment is more 

 than half the entire length of the cephalothorax and abdomen 

 combined, and its breadth is about one and one sixth times 

 the length ; the abdomen is very short, and, including the 

 caudal stylets, is scarcely equal to one fourth of the length 

 of the cephalothorax. Anterior antennae stout, seventeen- 

 jointed, but the second joint from the base appears to be 

 formed of two (or three) coalescent joints ; the proportional 

 lengths of the joints are shown by the formula — • 



40 ■ (19 ■ 10 . 7) ■ 8 ■ 10 . 12 ■ 16 . 9 ■ 9 . 16 . 12 ■ 1-2 ■ 12 ■ 12 . 16 . 18 . 8 ■ 26 

 1 2 3 4 5 b 7 8 9 10 11 12 13 14 15 16 17* 



The mandibles are stylet-shaped, stout, and elongate ; the 

 mandible-palp consists of a single oblong joint, the length of 

 which is rather greater than twice the breadth, and three 

 stout, moderately long, and nearly equal setae spring from 

 its truncate apex. The maxillas are composed of two parts 

 of nearly equal length ; the one part (the primary) is sub- 

 triangular in form and furnished with three apical setse, while 

 the other (the secondary part) is narrow, cylindrical, and pro- 

 vided with four seta3 at the apex (fig. 13). The basal 

 joint of the anterior foot-jaws is stout, but the end joint is 

 slender and curved and forms a claw-like appendage. The 

 posterior foot-jaws are nearly as in Dermatomyzon nigripes 

 (Brady and Robertson). The swimming-feet are also some- 

 wliat similar to those of that species : the fifth pair are 

 simple, two-jointed ; the first joint is short, and its breadth 

 is about equal to twice the length, it also bears a seta at the 

 upper distal angle ; the second joint is longer and narrower 

 than the first, its breadth being only equal to half the length, 

 and it is furnished with two setee at the apex. The caudal 

 stylets are nearly as long as broad, and equal to the combined 

 lengths of the last two abdominal segments. 



* Gibberuiu, huncli-backed. 



