Remains of a shore-crab (Fam. Cancridae) are found at three localities, in the Oamaru Series, in New Zealand; near Brighton, in Nelson and at Wharekuri in the Waitaki Valley. It has been described under the name of Harpactocarcinus tumidus ([Fig. 120 C]), a genus of the Cyclometopa or “bow crabs.”
Pleistocene Lobster.—
Numerous remains of a lobster, Thalassina emerii (see antea, Fig. 20), supposed to be of Pleistocene age, occur in nodules found on Queensland and North Australian (Port Darwin) beaches.
Eurypterids in the Silurian.—
The order EURYPTERIDA comprises an extinct group of Crustacea closely allied to the modern King-crab (Limulus). The body was covered with a thin chitinous skeleton, ornamented with regular scale-like markings. This group is represented in Victorian rocks by the remains of Pterygotus (“Sea-scorpions”), animals which often attained a length of six feet. Pterygotus (see Fig. 121 A) had the fore part of the body fused, forming the cephalo-thorax, which was furnished with anterior, marginal facetted eyes and central ocelli or smaller simple ones. To the ventral surface of the body were attached six pairs of appendages. The first pair are modified antennae with pincer-like terminations, used for prehensile purposes. Then come four pairs of slender walking feet. The sixth pair of appendages is in the form of powerful swimming feet or paddles, at the bases of which are the comb-like jaws. The abdomen consists of thirteen joints, the last of which, the telson, is spatulate and posteriorly pointed. Fragments of a tolerably large species of Pterygotus occur in the Silurian shales of South Yarra, Melbourne, Victoria. It was probably about 18 inches in length when complete. Of this form, known as P. australis ([Fig. 121 B]), portions of the chelate (clawed) appendages, and parts of the abdominal segments have been found from time to time, but no complete fossil has yet been discovered.
Fig. 121—SILURIAN EURYPTERIDS.
A—Pterygotus osiliensis, Schmidt. I. of Oesel. (After Schmidt)
B—Pterygotus australis, McCoy. Part of a body-segment. Silurian (Melb.) Victoria
Jurassic Insects.—