38 Description of Genera and Species. 



p. 367^ of his description that "the narrow longitudinal plates are the edges of a short 

 carapace " which shows a corresponding doublure, but is not serrated along its outer 

 margin as it would be if it belonged to a member of the present genus. The tail, as 

 shown by Woodward (pi. iv., fig. 10), is very much like those of A. grossarti and 

 A. russellianus. The telson appears to have been constricted and to have expanded 

 again near its tip, and its margin seems to have been denticulated and lobulated, and 

 the uropods similarly broadened. The arch of the tail segments and the form of the 

 epiniera are all much as they are in Anthrapalcevion. There can be little doubt that the 

 Pygocephalus of Huxley ought to take a place in the Schizopod family Lophogastridse, 

 and it shows how acute were the perceptions of Huxley that he compared his forms with 

 the recent Mysids, as he was not then aquainted with the structure of the recent Lopho- 

 ijaster, which was only described in the previous year by M. Sars" and was for long after 

 the only known member of the group. Since then, other genera have been discovered 

 and described and are now ranged under the family of the Lophogastridte, by G. 0. Sars, 

 the distinguished son of a distinguished father. Pygocephalus huxleyi H. Woodward, 

 at first placed under this genus by Huxley^ and afterwards described under the specific 

 name by Dr Henry Woodward,* who, however, was doubtful of its generic relationship, 

 if one can judge from the figures, is manifestly not a Lophogastrid, but belongs to the 

 Schizopod family of the Euphausiida3, and, as will appear in the sequel, is probably a 

 species of the genus Crangopsis [Palceocrangon'\ of J. W. Salter (pi. xi., fig. 8). The 

 tail of a form, however, probably nearly allied to Pygocephalus cooperi, was described by 

 Dr. Henry Woodward under the name of Necroscilla icilsoni,^ who considered that it had 

 affinities with the Squillids. The specimen figured represents the last five tail segments 

 and the tail fan enlarged 3 diameters. There is the same flattened, though perhaps 

 slightly more elongated form, as in Pygocephalus, the telson is serrated or lobulated and 

 carries two heart-shaped plates articulated with it in the position usually taken up by the 

 accessory swimmerets that were so common in these Carboniferous Lophogastrids. The 

 test is smooth as in Pygocephalus. The specimen is from the Coal Measures of Derbyshire. 

 It is perhaps a coincidence ; but it may be of zonal value, viz., that all the specimens of 

 Anthrapakcmon, as now restricted, and Pygocephalus, are from the Coal Measures, the 

 only shortened flattened form known from the Lower Carboniferous strata being Pseudo- 



' Quart. Jouin. Geol. Soc, 1857. 



- Forhand. Skand. Natiiif., Mode i., Christiania, 1856, p. 160. 



'Quart. Journ. Geol. Soc, 1862, vol. xviii., p. 421 (woodcut). 



'Trans. Geol. Soc. Glasgow, 1867, vol. ii., pp. 243-245, pi. iii., fig. 3 and woodcuts 1 and 2. 



° Quart. .Toiun. Geo!. Soc , 1879, vol. xxxv., p. 549, pi. xxvi., fig. 3. 



