the Morphology of the Biastoidea. 421 
tions seem to have escaped the notice of both Wachsmuth 
and Hambach. The other figure, published by the latter 
author, professes to represent the summit of P. sulcatus, and, 
though small, is clear enough to show that the “zigzag plicated 
integument ’’ which passes round the ovarian openings from 
one ambulacral field to the other is nothing but the crenula- 
tion on the central ends of the deltoid pieces. This is excel- 
lently shown in Rémer’s figures of P. crenulatus *, and also 
its continuation up onto the lancet-piece along the margins 
of its median groove. In all the best-preserved specimens of 
Pentremites that I have seen, the edges of the minute trans- 
verse grooves .on the ambulacral fields, which join their 
median grooves alternately on opposite sides, are also crenu- 
lated, as is shownin Dr. Hambach’s figure. But the markings 
are not due to the presence of any probably elastic “ integu- 
ment” overlying the plates, as Dr. Hambach seems to suppose, 
as they are merely delicate surface-ornamentation. In the 
case of the lancet-plate of Granatocrinus this is very well 
seen on ambulacra from which the pore-plates have disap- 
peared; so that the contrast between the crenulated edges to 
the median groove of the plate and its smooth peripheral 
portion is very marked. 
It is very singular that, although Dr. Hambach has “ had 
an opportunity to study a large and excellent material... . 
numbering several thousand specimens in almost every stage 
of preservation,” he does not make the slightest mention of 
the minute plates which have been described by so many 
authors as covering in the ambulacral furrows of the Blastoids. 
He is less reticent, however, about the so-called summit- 
plates, which are generally supposed to have roofed in the 
peristome, and to represent on a small scale the vault of the 
Palzocrinoids. or he says that the acute points of the zig- 
zag plicated integument, ‘‘ which almost come in contact with 
each other at the summit, are the only covering of the central 
opening, which was never closed by additional plates, as inti- 
mated by some authors ¢ ; although specimens are frequently 
found (and I have such in my collection) where it appears as 
if the summit were closed by additional plates, which on close 
examination, however, prove to be Bryozoa or ovulum-like 
bodies. Again, it seems improbable to suppose that the cen- 
tral opening was closed if we compare our fossils with Hehino- 
derms, with which they have unquestionably most affinity, 
both as regards the calcareous shell as well as the interior of 
* Wiegmann’s Archiv, Jahrg. xvii. Band i. fig. 15 (1851). 
+ Billings and Shumard. 
