Vol. 5 2. J ANNIVERSARY ADDRESS OP THE PRESIDENT. XCix 



Nova Scotia, illustrate the abundance of these small Crustacea in 

 the Carboniferous period. They have many points in common, but 

 probably deserve more than specific differentiation. 



With the exception of Anthrapcdcemon ParJcii, A. Traquairii, and 

 A. Etheridgei, which measure from 3 to 5 inches, the other species 

 do not exceed 1 to 2 inches in length. 



The carapace and body-segments were evidently and usually 

 broadly expanded, as in the Eryonidae ; the large scale at the base 

 of the outer antennae suggests the Penaeidae; the strong basal 

 joints of the inner pair of antennas with bifid flagella, and the outer 

 pair with single ones, are like many of the modern Caridea and 

 Astacidea ; the caudal appendages forcibly recall the rhipidina of 

 the living Galatheidae, in which,, as in some ancient forms, there 

 are two additional broad lamellae to the tail-fan, developed one on 

 either side of the telson. [This fact, as Peach correctly observes, 

 strongly favours the view that the telson should not be treated as 

 a mere median appendage, but as a true 21st body-segment.] 



In the spinose ornamentation of the somites and caudal plates ; 

 in the broadening out of the segments of the abdomen and the short 

 rounded form of the cephalothoracic shield (especially in Anihro- 

 pcdcemon Parkii) one is reminded of the genus Squilla, but most 

 probably this is only an analogy and nothing more. There is some 

 evidence, though not quite satisfactory, that the branchiae may have 

 been partly exposed as in Mysis, but we need further light on this 

 point. 



Enough has been said, however, to show that the small Carboni- 

 ferous Crustacea are much more generalized than their modern 

 descendants, and probably stood in the position of great an- 

 cestors to most of the living Macrura and even to the Brachyura 

 also. 



The Caridea, embracing all the shrimps and prawns, and possibly 

 also some of those ancient Carboniferous species of Anthrapalae- 

 monidae already referred to, are divisible into the Monocarpinea, 

 the Polycarpinea, and the Crangonidea. 



Monocarpinea. — In this section the fifth joint of the wrist of the 

 second pair of thoracic limbs is not subdivided, and the chelae of this 

 pair are larger than those of the first pair. 



The living representatives are divided into eleven families, the 

 best known perhaps of which is that of the Palaemonidae, embracing 

 the true Prawns. In these the first and second pairs of thoracic 



