406 Dr. H. Woodward—On a Fossil Schizopod Crustacean. 
Measurements of the female of Pygocephalus (Fig. 6) :—Extreme 
length of the more perfect female of Pygocephalus, 40 millimetres ; 
breadth at base of antenne, 10mm.; breadth of caudal plates, 
where infolded towards base of thorax, 18mm.; greatest breadth of 
marsupium near the centre of thorax, 12 mm.; breadth in front, 8mm., 
posteriorly 10mm.; number of imbricated plates, 7 pairs; length, 
15mm. ; average length of plates, about 2mm. The outer margins of 
the scales of brood-pouch are straight, the inner borders roundly 
curved. Measured along its convexity, length of abdomen in 
Mr. Johnson’s specimen (I. 1536), 20mm.; length of telson, 10 mm. ; 
the margins of the 5 segments are recurved and their borders pointed. 
In the male Pygocephalus, in which the oostegites are absent, the 
central thoracic plates are usually somewhat hexagonal in form; 
with these the small marginal plates (bearing the coxopodites of the 
thoracic limbs) are intercalated. In some examples of Pygocephalus 
Fic. 2.—Pygocephalus (Anthrapalemon 2) Parkeri, sp. nov., H. Woodw. Coal- 
measures: Sparth, near Rochdale. Obtained by Mr. W. A. Parker, F.G.S., 
and presented to the British Museum (Natural History). x 2 nat. size. 
the central plates are more quadrate-oblong. These differences may 
also be noticed in Huxley’s figures of the thoracic plates of his two 
examples (Quart. Journ. Geol. Soc., 1857, pl. xiii, figs. la, 3, 
2, 3; also in our Plate XVIII, Fig. 3, and in Woodcut Fig. 1 in 
text). The telson and uropods in Huxley’s example are represented 
as truncated (op. cit., pl. xii, figs. la, 6). The telson of those we 
figure now are pointed (see Pl. XVIII, Fig. 4). But possibly 
the caudal plates of Figs. 1 and 6 from Mr. Hughes’ collection 
may have had a blunt and square telson with correspondingly 
