DESCRIPTION OF THE SPECIES OF PTERYGOTUS 239 
very slightly truncate at the posterior end. These plates are some- 
times four inches long and three broad, and are oval, the greatest 
width being less than half way from the notched end; flat on one 
side and of but slight convexity on the other, except at a point on 
the median line about one-third distant from the smaller end, where 
there is a prominence (probably the point of insertion). They are 
more covered with sculpture than in the species previously described. 
Fie. 11. 
Packets of eggs or ovisacs (Parka decipiens). No. 1 is from a specimen in the cabinet of 
Lord Kinnaird. 
(Parka decipiens, Fleming. See Siluria, 2nd ed. chap. 10.) These 
occur too often with Pterygotus not to be suspected as part of its 
structure, and are found with the P. anglicus in Forfarshire and Perth- 
shire ; also, with P. Zudenszs at Kidderminster, and P problematicus at 
Ludlow. 
Four fine specimens lent us by Dr. Balfour, of the Botanic 
Gardens, Edinburgh, show clearly that the bodies in question cannot 
be referred to seed vessels or receptacles, or indeed any other portions 
ofa plant. There is no trace of a style on any of the carpels of the 
supposed fruit, nor of a leafy involucrum below it. 
They are rounded masses, one to two inches broad, and composed 
of numerous oval or hexagonal arez, a line or two in diameter, which 
are now flat, but appear as if they had been compressed from a nearly 
