Contributions to Invertebrate Palaeontology. 569 



Macrouran Decapod, which appears to differ so much from any 

 described cfenus as to make it undesirable to refer it to any of them. 

 One of its peculiarities consists in the possession of a pair of very 

 strong antennal appendages, which project from beneath the anterior 

 end of the thoracic carapace, and are of such size and strength as 

 to raise considerable doubt as to their true nature. The existence 

 of five thoracic limbs, exclusive of these, projecting from beneath 

 the carapace on one side would seem to place their pedal nature out 

 of the question ; while their great development as seen on the speci- 

 men would Indicate that they had served some purpose other than 

 simple antennas, and to raise the question as to the possibility of 

 their having been chelate at their extremities. As only the basal 

 portions of these organs are represented, however, this question 

 cannot be satisfactorih" determined. Having had an opportunity 

 of consulting Dr. A. S. Packard, Jr., in regard to them, he gave as 

 his opinion, that from their position and the representation of the 

 other five pairs of thoracic members without them, they could not be 

 other than antennal in their functions, notwithstanding their great 

 size and anomalous character. Taking this view of their nature, 

 the specimen would conform strictly to the type of Macrouran 

 Decapods. 



In its generic relations, as well as in its general expression, the 

 specimen resembles most nearly the genus Pygocephalus of Prof. 

 Huxley, first given in the Quart. Jour. Geol. Soc. London, vol. 13, 

 p. 363, 1857, with figures and descriptions of three specimens, under 

 the name P. Cooperi. Neither the genus or the species were well 

 characterized at that time. It is however again referred to in vol. 1 8, 

 p. 420, of the same journal, with a figure of a specimen supposed to 

 be of the same species, much better preserved, from the coal shales 

 at Paisley. There are, however, too many limbs represented as 

 originating from the thorax for a Decapod, and the antennae, 

 although represented as of large size are not like those of the Ohio 

 specimen, while there is a second pair shown. In other parts the 

 figure is indistinct, and in the description the parts are not defined 

 sufficiently for close comparison. The difi'erences, however, are so 

 great that I shall propose for this form the new generic name 

 PALui;oPALiEMON, with the following diagnosis : — 



Annals N. Y. Acad. Sci., V, Jan. 1891. — 38 



