310 M. T. C. Winkler on 
divided transversely, or separated by an oblique hinge; all 
the specimens which present the caudal fin intact offer this 
peculiarity. Htallon mentions this division of the outer 
plates of the caudal fin in speaking of the Glyphee of the 
“terrain & chailles’” which he has examined; von Meyer, 
Oppel, and other naturalists also speak of them. Accord- 
ing to the figure of Arwosternus Wienecket, all the lamine 
of the caudal fin of this species are membranous in the 
inferior two thirds of their length, and calcified in the supe- 
rior third. M. De Man says, “The seventh segment (the 
telson) is quadrangular, a little longer than broad; the 
anterior third is calcified, and furnished with several tufts of 
short hairs, as on the margins of the other segments; the 
other part is membranous, with many longitudinal series of 
very small tufts of short hairs. The lateral lamellee of the 
sixth segment are broad, and form with the seventh segment 
the caudal fin ; their upper surfaces are covered with several 
longitudinal series of tufts of hairs, resembling those of the 
upper surface of the seventh segment.’”’ Moreover the seventh 
seoment of the abdomen of Arwosternus is of quadrangular 
form, while in the Glyphee this organ is in general more or 
less triangular. There is therefore a considerable difference 
between the caudal fin of the Glyphee and that of Areoster- 
nus Wienecket. 
These are the differences which separate the Glyphec from 
Areosternus. Now let us examine the analogies. 
On glancing at the figure of Glyphea Sceemanni, Opp., in 
pl. i. of the ‘ Paliontologische Mittheilungen,’ and at the 
same time at the figure of the natural size of the unique 
specimen of Arwosternus Wienecket, De Man, drawn by that 
naturalist himself, one is at once struck with the very great 
analogy or resemblance which exists between these two forms 
of Crustaceans. No doubt the habit of the one is also that of 
the other genus. 
Thecephalothorax of the G'lyphee is of an elongate cylindroid 
form. M. De Man says of the cephalothorax of his Arcoster- 
nus that it has an elongate subcylindrical form, and that its 
superior surface has an elongate rectangular form ; its greatest 
width, which occurs a little behind the cervical groove, is in 
proportion to the length as 5to 8. ‘The front of the Gly- 
phec is not much pointed; and at its sides there are seen the 
two sinuses which lodge the ocular peduncles. In Arcoster- 
nus, according to M. De Man, we observe a broad triangular 
front, slightly curved downwards. It is separated from the 
external angles of the cephalothorax by two deep triangular 
incisions, in which the eyes appear. The posterior margin 
