Vol. 52.] ANNIVERSARY ADDRESS OF THE PRESIDENT. CVli 



a small carapace, compressed on the sides ; the eye-stalks are small ; 

 both pairs of antennae have long peduncles. The first pair of legs 

 are imperfectly chelate and expanded for digging at their 

 extremities, the others are shorter and hirsute. The swimming- 

 plates of the tail are slender and pointed. 



The Thalassinae are common on the west coast of Australia and 

 in the Fiji Islands, and always inhabit deep burrows, which they 

 excavate in the sand or mud near low water. One fossil species, 

 Th. Emeryi (Bell), has been described by Prof. Bell from Western 

 Australia, where Th. scorpioides is found living. 



The genus Callianassa (belonging to the same family) occurs on 

 the coasts of Ireland, Britain, France, and the Mediterranean, the 

 shores of North America, and elsewhere. The carapace is small, 

 without a rostrum ; the abdomen large ; the integument is not very 

 firm. The front legs are large and strong, one hand being very 

 much more developed than the other ; the third pair of legs are 

 wide near the end, and are used by the animal in digging. 



This lobster lives habitually concealed in its burrow with only 

 its strong chelate fore-limbs projecting, ready to seize on any passing 

 prey. As a result of this habit, perfect specimens are seldom to be 

 obtained, but the great claws are frequently to be seen, both 

 recent and fossil, in Museums. 



A species of the genus Callianassa is met with in the Kimme- 

 ridge Clay ; one species occurs in the Cretaceous of North America, 

 ten in that of Europe, and one in the Eocene of the Isle of 

 Wight. So far as one is able to rely upon the imperfectly preserved 

 fossil remains, it would appear that the species of this genus have 

 undergone but little change, and occupy to-day the coasts of 

 relatively the same areas in which their fossil remains have been 

 found as far back as the Upper Jurassic. 



Upogebia (=Gebia) is an equally active burrowing form, and 

 closely related to Callianassa, from our own shores and those of 

 North America. Passing over the Axiidae, also closely related, we 

 come to the Thaumastochelidae, established for the genus Thaumasto- 

 cheles, a very remarkable burrowing form dredged from 450 fathoms 

 and more, off St. Thomas, in the West Indies, by the Challenytr 

 Expedition. It is very like the Callianassidae in general appear- 

 ance, but one of the hands is modified into a very strong claw, armed 

 with a long, slender, and delicate forceps-like chela provided with 

 slender and very numerous teeth. This curious burrowing form of 

 Crustacean (Thaumastocheles Zaleucus), living now in deep water 



