REPORT ON THE CRUSTACEA MACRURA. 711 



Milne-Edwards describes the genus as having the second pair of gnathopoda small 

 in size and very narrow. Dana describes it as being suboperculiform, which corresponds 

 more nearly with the condition in our species. 



Milne-Edwards also says that there are five well-developed branchial plumes on each 

 side, and that those attached to the oral appendages are rudimentary. Dana says that 

 in Pontonia tyrrhena there are but four branchiae on either side of the pereion, and that 

 there are none attached to the fifth pair of pereiopoda. 



In our specimen there are four pairs of pleurobranchiaa, that belonging to the 

 posterior somite being wanting. 



This description may be reconciled with that of Milne-Edwards, since it is evident 

 that what he describes as a branchia attached to the oral appendage, and therefore 

 rudimentary, is what I have described as a mastigobranchial appendage connected with 

 the posterior pair of siagnopoda (or maxillipede). 



The branchial apparatus in this species consists of four pleurobranchial plumes on 

 each side and may be tabulated as follows : — 



Pleurobranckiae, . . .... 



Artlirobrancbiaj, . . .... 



Podobranchia?, . . . .... 



Mastigobranchise, . . .... 



h 



The original description of Dr. W. Peters was communicated to the Academy of 

 Berlin February 18, 1851, but so far as I can ascertain was not published until 1852, 

 the same year that Dana published his description of Pontonia tridacnse, which is 

 probably the same species, and I am inclined to think from the description that 

 Conchodytes mdeagvinze, Peters, taken at Ibo on the Mozambique coast, is probably 

 the same species as the Challenger specimen, Pontonia meleagrinse. from Torres Strait. 



Our specific name was in type before I was aware of Peters' or Hilgendorfs 

 memoirs. Peters' specimen was a female, 33 mm. long, and like ours was probably 

 found in the pearl-oyster, hence the coincidence of its specific name. 



Family Pal^emonid^e. 



Carapace dorsally rounded and laterally compressed. Eostrum long, laterally 

 compressed, and generally armed with teeth. Pleon laterally compressed. Telson long 

 and gradually narrowing to a truncated extremity. Ophthalmopoda well developed and 

 pyriform. Antennas long and slender ; first pair having the first joint of the peduncle 

 hollowed on the upper surface, carrying a well-developed stylocerite on the outer side, 

 and terminating in two flagella, of which one is frequently branched ; second pair 

 furnished with a long and narrow foliaceous scaphocerite, the outer margin of which is 



