REPORT ON THE CRUSTACEA MACIM'UA. 119 



The first pair of antennas has three short joints to the peduncle and the remains of a 

 slender niultiarticulate flagellimi, to which 1 have given its probable length as well as ;i 

 second branch, because I am not aware of any species of Macrura that has not a second 

 flagellum attached to the first pair of antennas. 



The second pair of antennas has very little of it represented in the specimen, but it 

 evidently carried an ovate scaphocerite ; that on the right side of our figure is half lost, 

 whereas of that on the left there is the impression only ; the rest of the organ is wanting 

 on each side except what I take to be the impression of the distal joint of the peduncle, 

 and the first articulus of the flagellum on the right side. 



The first pair of large chelae is well shown on the right side, although part of it is 

 expressed by the impression only. That on the left I have restored in outline from 

 that of a specimen of Polycheles crucifera, in order to show the near resemblance of the 

 same part in the two genera. 



All the other appendages are lost, or hidden beneath the body of the animal, ex- 

 cepting those that go to form the rhipidura, the outer plates of which are only determinable 

 by the impression left on the rock. They are broad, leaf-like, and rounded at the 

 extremity, without any sign of a diaeresis or division in the outer plate, or a tooth at the 

 outer distal angle ; telson is broad at the base, and tapers abruptly to the extremity. 



This species bears a generic resemblance to Polycheles of the recent seas, especially to 

 Polycheles crucifera, in the form of the carapace, although it is deprived of its strong 

 lateral armature, of which a trace only remains at the posterior branchial margin. 



It bears, however, a nearer resemblance to Polycheles helleri and Polycheles baccata 

 in the form and breadth of the pleon, but differs from all in the absence of a prominent 

 longitudinal carina which is conspicuous in most of all the known recent species of 

 the Eryonidae, excepting the genus Eryoneicus, on the median dorsal surface of the 

 pleon. 



The fossd also differs from the recent species of the same family in having a broad 

 and open orbital notch, instead of a narrow cleft in the dorsal surface of the carapace, 

 which is filled up with the upper surface of the base of the rigidly attached ophthalmopod. 



The first pair of antennae, so far as I am able to interpret the evidence at my dis- 

 posal, has not the inner margin of the first joint of the peduncle produced to an elevated 

 ridge, a circumstance that is largely due to the distance at which these appendages are 

 separated from each other. 



The second pair of antennae, if I understand correctly the parts represented in the 

 specimen, approximates more nearly to the recent forms than to those of any fossil Eryon 

 that I have met with, differing from the latter in carrying a distinct scaphocerite at the 

 base. It is true Desmarest states that the second pair of antennas is provided with a 

 large scale, but he does not show it in his figure of the animal, and although it has been, 

 I believe, generally accepted by authors who have written on the subject, I am not aware 



