Clypeo antice attenuato, plano; oculis rotundis, proximis; cauda ovata, acuminata.
The head of this species is much more elongated than it is in the two preceding species. The anterior portion of the buckler is much prolonged. The eyes are approximate, rounded, and near the posterior edge of the head. The abdomen is furnished with eight distinct articulations; the middle lobe is scarcely broader than the lateral lobes; tail rather broader than the head, and ovate; posterior termination more rounded than the buckler. Length nearly three inches.
The specimen from which our model was taken belongs to the Albany Museum. No label is attached to it, but I was informed by Mr. Meach, one of the proprietors, that it was found in the western part of the State of New York. It is embedded in an ash-coloured limestone. The specimen is a good deal worn—but the peculiar form of the eyes, and the narrowness of the middle abdominal lobe, clearly distinguish it from either of Dr. Dekay's species.
Isotelus Megalops.[40] Green. Cast No. 25.
[40] From the Greek for "great eyes."
Clypeo antice subrotundato, postice arcuato; oculis magnis, rotundis, eminentissimis; cauda suborbiculari, limbo lato; articulis abdominis octo.
The buckler in its contour resembles very much the head of the I. gigas; it is, however, rather more rounded before, and arcuated behind. The oculiferous tubercles, are very peculiar, being very large, round, and exceedingly prominent. They have a good deal the appearance of solid hemispheres placed on the forehead of the animal. They are exactly on a line with the two abdominal furrows. The abdomen is composed of eight distinct articulations; the middle lobe is rather larger than the lateral lobes. The tail is suborbicular, convex, and rather less than the head. Length nearly five inches. Breadth almost three inches.
This magnificent Isotelus was obtained near Trenton Falls, in New York, by P. A. Browne, Esq., and now forms a part of his fine collection of fossils, in this city. It occurs in black transition limestone. It differs essentially from the I. gigas of Dekay, in the magnitude, collocation, and contour of the eyes. Those of the I. gigas are oblong and lunate, and nearly half the distance between the anterior and the posterior edges of the buckler; those of the I. Megalops are not only much larger, but they are round, and very near the posterior border of the head.
Isotelus Stegops.[41] Green. Casts Nos. 26 and 27.
[41] From two Greek words, which signify "covered eyes."