212 Part III. — Twenty -fifth Annual Report 



and moderately stout terminal appendages, one of which forms a short 

 hook-like process, while the other is straight and terminates in two 

 slender setse of unequal length (fig. 12). 



The structure of the fourth pair appears to be similar in the two sexes ; 

 the outer branch is moderately slender and elongated, and composed of 

 three sub-equal joints armed with long spiniform seta? on the outer 

 margin ; the inner branch is very short and two-jointed, the first joint 

 being extremely small, while the second is slender and moderately 

 elongated, and furnished with three small terminal setae (fig. 13). 



The fifth pair in the female consists of a small basal joint to which is 

 articulated a narrow elongated plate about four times longer than broad, 

 and provided with a number of setae arranged as shown in the drawing 

 (fig. 14). In the male the fifth pair is similar to those of the female, but 

 smaller and less spiniferous (fig. 15). 



The furcal joints in both the male and female are elongated and 

 slender and set widely apart ; they are each furnished with a long and 

 stiff apical bristle and a few small hairs (see fig. 6). 



I have obtained this species in the same situations with the Harrietella 

 previously mentioned, but it seems to be a rarer form, and males 

 especially appear to be very scarce. 



Notodelphyoida, G. 0. Sars. 



Fam. Doropygidce. 



Genus Notopterophorus, Costa. 



Notopterophorus papilio, Hesse. PI. xiv., figs. 1-19. 



1865. Notopterophorus papilio, Hesse. Observations sur des 

 Crustaces rares ou nouveaux des cotes de France, Ann. des 

 Set. Nat, 5th Se>. zool., vol. i., p. 338, pi. xi., figs. 1-13. 



1878. Notopterophorus papilio, G. S. Brady. A Monograph of 

 the Free and Semi- parasitic Copepoda of the British Islands 

 (The Ray Society), vol. i., p. 142, pi. xxxi., figs. 3-12. 



The Entomostracan to which M. Hesse has given the name mentioned 

 above is one of the most remarkable among a strange group of species 

 found living as " unbidden guests" within the branchial chamber and 

 sometimes in the alimentary canal of various simple and compound 

 Ascidians. 



The distinguishing characteristic of Notopterophorus is, as the name 

 implies, the peculiar wing-like appendages of the cephalo-thorax, which 

 give to the creature its somewhat grotesque appearance. These append- 

 ages, which are situated on the dorsal aspect, appear to be six in number, 

 and assume the form of very thin and almost transparent plates, each of 

 which terminates in long, slender, whip-like filaments. The frontal 

 plate, which is obscurely triangular, has a hood-like structure, and 

 appears to be furnished with three filaments — one central and one at 

 each of the lateral extremities ; this plate seems to be an expansion of 

 the first thoracic segment. The next four plates occur in pairs ; the 

 first pair spring from the second segment of the thorax, and the following 

 pair from the third segment, and each single plate bears two whip-like 

 filaments. The posterior plate, which is of one piece, moderately large 

 and broadly triangular, and which springs from near the distal end 

 of the last segment of the thorax, is apparently provided 



