REPORT ON THE CRUSTACEA MACRURA. 473 



Division PHYLLOBRANCHIATA. 



The species of Macrura in this division consist of all those which possess a series 

 of branchial plumes, developed in the form of broad foliaceous plates of extreme tenuity, 

 attached to a central stalk. 



They may conveniently be divided into those which are normal in their characteristic 

 features, and those in which there is a greater or less aberrant departure from the more 

 perfect structure. 



Group ABEREANTIA. 



This group consists of several tribes and families that in their adult condition 

 approach more nearly to the characters common to other divisions, but which nevertheless 

 during the progress of development pass through a stage common to the normal 

 Phyllobranchiate Macrura. 



This aberrant group has long been distinguished by carcinologists under the name of 

 the Anomura, sometimes as a division of the Macrura, and sometimes as a distinct order. 

 It is as a separate group of the former that they are here noticed ; for undoubtedly in 

 their earlier stages they pass through a morphological change that is essentially 

 Macrurous, in which the scaphocerite and rhipidura are both present as well-developed 

 appendages, the latter of which they never entirely lose. 



The acknowledged species of this group belonging to the Challenger collection 

 will be reported on by Professor John R. Henderson, M.B., F.L.S, 1 but there are two 

 or three immature specimens that appear to me not to belong to the normal forms of this 

 division, and I have arranged them under this group, assuming that in their mature con- 

 dition they may belong to some unknown aberrant species. 



Zoontocaris, n. gen. 



Carapace less than one-third the length of the animal, not covering the entire pereion, 

 and anteriorly produced to a long rostrum that is broad at the base and sharp at the 

 apex. 



First somite of the pleon little broader than the succeeding ones. 



Telson gradually increasing in width posteriorly and terminating in a sharp tooth at 

 each angle. 



Ophthalmopoda subpyriform and projecting laterally and posteriorly. 



First pair of antennae biflagellate. 



1 Zool. Chall. Exp., part lxix. 



(ZOOL. CHALL. EXP. PART LII. — 1887.) Fff 60 



