SLIMONIA ACUMINATA. Ill 



compared with Slimonia, and probably that the food of the former consisted of quick- 

 swimming fishes and cephalopods, whilst the latter preyed upon minute or sedentary animals, 

 or was possibly a carrion-feeder, like so many of its representatives at the present day. 



If we really knew such to be the actual function required to be performed in each 

 case, the organs in question could hardly be better adapted for their respective tasks. 



Endognaths (= Mandibles and Maxillae) (PI. XVII, figs. 1, 3 , 4, 5, fig- 4 ; and PI. 

 XVIII, figs. 1, 3, 4, 5). — Following next after the antennae we find three pairs of endo- 

 gnaths, with a pair of eight-jointed palpi to each. There is a very good woodcut (fig. 7) of 

 one of these on p. 62 of the Survey Memoir on Pterggotus, and upon p. 63 of the same 

 work is a woodcut of a head with parts of two of the palpi preserved nearly in situ. 



We figure a large detached endognath on PL XVII, fig. 4, the palpus of which 

 measures four inches in length. 



The coxa or basal joint (co) is roughly quadrangular in outline, and is 1^ inches 

 in both length and breadth ; the inner border {g) is 8 lines broad and is armed with 

 about fourteen sharp and curved teeth, which at the upper end are nearly 2 lines in 

 length, but diminish rapidly to the lower part of the mandible, where they are little more 

 than bristles (as in the endognath of Limulus) ; the lower border {b) is nearly square, but 

 half an inch narrower than the upper border ; by it the appendage was attached to the 

 head ; a few scattered scale-markings are disposed over the upper free border. 



The palpus (b-u) in this specimen seems to be turned the reverse way ; it lies with its 

 spiny border downwards and its point directed outwards ; usually its upper border is 

 spinose and the recurved terminal spine is directed inwards, as in the accompanying wood- 

 cut, fig. 32, p. 112. 



The basos (b) is an oblong joint one inch in length and three quarters of an inch 

 broad ; it has a few scale-markings on its upper border. 



The ischium (i) measures one inch along its longest border, but only half an inch along 

 its spinose upper border, being sharply bent upwards ; it is three quarters of an inch 

 broad. 



The meros (m) is three quarters of an inch long and the same broad ; its distal end 

 and that of the four succeeding articulations is fringed with spines. 



The carpus (c) is three quarters of an inch long and seven lines broad. 



The propodos (p) is five lines long and six broad. 



The dactglus {d) is three lines long and four broad. 



Between this joint and the terminal claw (u) there is a small joint (t) two lines long 

 and four broad (seen also in the woodcut, fig. 32, p. 112); the claw (u) is half an inch 

 long, and strongly recurved. 



The accompanying woodcut (fig. 32, p. 112) represents the largest endognathary palpus 

 with which I am acquainted. It measures seven inches in length and two inches in greatest 

 breadth. The five distal joints appear to have been fringed with spines at their lower and 



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