The buckler is regularly lunate; the margin is slightly reflected or raised anteriorly, the posterior edge forms a continuous rim, running nearly parallel with the articulations of the abdomen. The front on each side has one large and two small tubercles, near its superior edge. The oculiferous tubercles on the cheeks are on a line with the lowest frontal tubercle. There are fourteen distinct articulations; but as the tail is mutilated and distorted, the total number of joints cannot, from this specimen, be ascertained. The body appears to have been covered with small pustules. These are very evident on the front. Costal arches simple, or not grooved. Length, one inch and three-fourths, breadth of the buckler one inch and one-fourth.
This species resembles a little the C. Pulchella of Dalman. The specimen from which the model was taken, is in the possession of Mr. R. Peale, of New York, who willingly lent it for this monograph. He informed me that it was found in the state of New York, but he was unable to name its precise locality. It occurs in a soft ash coloured limestone. No other petrifaction is observable in the fragment of rock which contains it.
Calymene Platys.[16] Green. Casts No. 4 and 5.
[16] From a Greek word which signifies Flat,
Clypeo antice rotundato; prominentia frontali utrinque quatuor tuberculis.
The buckler is probably semilunate; but as the anterior portion is lost, this cannot be determined with precision. The posterior raised rim is not continuous, as in the C. Selenecephala, but is separated by the longitudinal dorsal furrows. The front is distinctly divided from the cheeks, and has four tubercular prominences on each side. Three of them are nearly on a line with the lateral edge of the cheeks, and gradually diminish in size, as they descend to the anterior part of the buckler. The other is smaller, and is between, and a little to the side, of the upper two. The cheeks form spherical triangles. The oculiferous prominences are close to the second large tubercle on the front. The cheeks are, however, quite imperfect. The articulations of the back cannot be distinguished from those of the tail. In our specimen they are all beautifully distinct, and are twenty-two in number. The posterior raised rim of the buckler seems to form an articulation; its extremities on each side are a good deal thickened and expanded. The costal arches suddenly curve downwards and backwards, near their middle, so as to divide the abdomen and tail into five unequal sections. The whole length is nearly three inches. The breadth of the buckler nearly two inches.
This fine large Calymene was accidentally discovered on the Helderberg mountain, by my friend, Professor T. R. Beck. One of the loose pieces of sandstone rolling over, near his feet, presented him the fine natural mould, from which he has kindly permitted our cast to be taken. The animal relic once enclosed in this matrix, must still be near that locality, and yet remains undiscovered, to reward the enterprise of some more fortunate naturalist.
One of our models represents the natural mould found by Dr. Beck. The other is a cast taken from it and exhibits, more satisfactorily, the various parts of the animal.
Calymene Microps.[17] Green. Cast No. 6.
[17] From the Greek for "small eyes."