204 GEOLOGY AND MINERALOGY. 
SCIENTIFIC AND LITERARY NOTES. 
GEOLOGY AND MINERALOGY. 
AGELAORINITES BILLINGSII. A NEW SPECIES. 
PRELIMINARY NOTICE OF, BY E. J. CHAPMAN. 
Mr. W. M. Roger, an undergraduate of the University of Toronto. and one of 
our most esteemed students, lately submitted to us a collection of fossils obtained 
by him from the Trenton Limestone of Peterboro’, Canada West.} Amongst these, 
we discovered an undescribed species of the rare and interesting-genus, Agelacri- 
nites. We propose shortly to publish a complete description, with a figure, of 
this new species ; but beg, in the meantime, to bestow upon it the above specific 
name, after the distinguished paleeontologist of our Geological Survey, who has 
contributed so pre-eminently to our knowledge of the peculiar group of forms to 
which the genus Agelacrinites belongs, or to which it is closely related. Our 
specimen presents a flat, cireular form, exactly half-an-inch in diameter. It has 
five straight, or nearly straight, rays, composed of a double series of interlocking 
or alternating plates, and terminating in well defined rounded points, about one 
line from the margin of the shell or test. In the @entre of the dise where the 
mouth is usually thought to be situated, there are five comparatively large and 
somewhat rhombic plates, the first ray-plates, one being common to each two ad- 
jacent rays. In the space between two of the rays, and at a distance of about. 
two lines from the centre of the test. there is a well-marked “anal-pyramid” (or 
“ ovarian aperture ’) surrounded, apparently, by ten plates: five being situated in 
alternate positiou within the other five, exactly as in Hall’s Hemicystites parasi- 
tica (—Agelacrinites parasiticus). All the other portions of the inter-radia} 
areas, with the margin of the test, are covered by imbricating or partially- 
overlapping and irregularly disposed plates of various sizes. At the margin there 
are about three or four rows of very small and exceedingly numerous plates, 
narrow and pointed, and succeeded by larger plates, of which the greatest diameter 
(unlike that of the marginal plates) lies pavallel to the circumference. These are again 
succeeded by somewhat smaller and more pointed plates. A. Billingst? differs 
most obviously from A. Dicksoni, the only other Canadian species yet recognised 
(if we allow the Hdrioaster of Billings to be a thoroughly distinct genus), by the 
possession of straight in place of curved rays, and by its exceedingly numerous 
marginal plates. It agrees much more nearly with the Niagara limestone species, 
A. parasiticus (Hail’s Hemicystites parasitica); but from this it is distinguished 
essentially by the width of its rays (and by the ray-plates) being largest in the 
centre of the dise, and by the rays terminating in well- defined rounded points. 
In Hall’s species, the rays are quite narrow and close together at the centre, and 
they broaden outwards, and, to use Professor Hall’s language, “ coalesce with the 
plates of the body ;” or, in other words, are altogether undefined at their extremi- 
ties. These characters are exactly the reverse of those which obtain in A. 
Billingsi. Besides which, in Hall’s form there appears to be only a single row of 
small border-plates, but that is probably an uncertain character. The other dig- 
