170 COPEPODA. 



Antennae moderately stout, outer ranius slender, elongated 

 and biarticulate (PL XVIII. fig. 6). 



Mandibles narrow; basal joint of mandible-palp dilated, 

 and furnished with two moderately long branches of nearly 

 equal length, the lower one being armed with two strong 

 spines situated in the middle of the external margin, in 

 addition to several setse, as shown in the drawing (PL X. 

 fig. 17). 



The second maxillipeds are stout and armed with a mode- 

 rately short terminal claw (PL XIII. fig. 10). 



The first pair of thoracic feet are moderately short and 

 robust; the outer ramus, which is considerably shorter than 

 the inner, is furnished with tolerably long spiniform and 

 coarsely plumose marginal setse ; the inner ramus is two- 

 jointed ; the first joint is longer than the entire outer ramus, 

 and is strongly dilated interiorly, but tapers towards the 

 distal extremity ; the end joint is small and armed with a 

 stout but tolerably short terminal claw and an elongated 

 seta (PL XIV. fig. 9). 



The second, third, and fourth pairs are somewhat similar 

 in structure to the same appendages in Dactylopusia tisboides. 



The fifth pair are tolerably large; the basal or primary 

 joint forms a broad quadrangular plate armed with five stout 

 spines or spiniform setse arranged as shown in the drawing 

 (PL XX. fig. 4) ; the external margin is deeply notched 

 near the middle, and to this notch the small secondary joint 

 is articulated, this joint is narrow and is provided with two 

 short stout setse on the outer edge, two at the apex, and a 

 small seta on the inner edge. 



Furcal joints short. 



Habitat. Salcombe, Devon ; a single specimen was found 

 in a gathering collected at this place in June 1875. 



The form now described resembles generically two species 

 of Dactylopusia (D. laticaudata and D. cemula), recently 

 described by I. C. Thompson and A. Scott, in their Report 

 on the Copepoda collected by Professor W. A. Herdman at 

 Ceylon in 1002 * ; these species will now be included in the 

 same genus with that described here, viz. Megarthrum. 



It should be mentioned that in their remarks on these two 

 Ceylon species the authors stated that both might some time 

 or other require a separate genus for their reception, 



* Report to the Government of Ceylon on the Pearl Oyster Fisheries 

 of the Gulf of Manaar, by Prof. W. A. Herdman. Supplementary 

 Report VII. (Copepoda), by I. C. Thompson and A. Scott (pub. by the 

 Royal Society, 1UU3), p. 27'l. pi. xi. fig-s. 1-8; aud fig's. 9-12. 



