On the "Seraphim" and its Allies. 233 



basal joints serve the office of palpi. The two first pairs of 

 organs are chelate. The eyes are six to eight in number, and 

 are placed, two near the centre, and two or three upon each an- 

 terior angle of the carapace. The body segments are robust, 

 and the tail long and narrow, and terminated by a cordiform 

 tail-plate, finely pointed at its tip. The reproductive organs 

 are placed immediately behind the mouth ; but as the scorpions 

 belong to the Arachnida (a division of the Insecta, which, 

 although closely approaching the Crustacea, is distinguished 

 from them by always breathing by means of tracheal, whilst 

 the latter are furnished with branchial), we must seek for true 

 affinities among the Crustacea, properly so called. 



In Limulus the true organs of locomotion may be said all to 

 belong to the cephalothorax, and are arranged around the 

 mouth, their basal joints serving the office of palpi and man- 

 dibles (see woodcut, Fig. A.). The abdomen is furnished on its 

 under side with a series of lamellae ; the firsb of which (Fig. B) 

 overlaps and nearly conceals the succeeding five. They are all 

 exactly like the upper one externally ; being, in reality, only a 

 modification of the abdominal swimming feet of the lobster and 

 other Macrura; but the first is said to belong to the thorax, and 

 carries upon its inner surface the reproductive organs (Fig. B, a), 

 whilst the five which succeed it support and shield the branchial, 

 or gills. These organs of respiration are constantly vibrating 

 during life, as may be seen in the specimens kept in the fish- 

 house of the Zoological Gardens. The eyes are placed on either 

 cheek, upon the upper surface of the horseshoe-shaped cara- 

 pace, very much as in the Trilobites. They are compound, and 

 present a beautiful facetted structure when seen through a 

 pocket-glass. Two larval eye-spots may also be detected in 

 the centre of the carapace* in front. Although the shell of 

 Limulus appears to be composed of only two parts — the one re- 

 presenting the cephalo-thorax, and the other the abdomen, 

 terminated by a long, powerful, spine-like appendage — yet, on 

 examining it carefully beneath, we see traces of sutures, indi- 

 cating the division of the abdomen into five separate segments, 

 as in many other Crustacea. f 



The first organs of Limulus are a pair of small cheloi placed 

 in front of the mouth (woodcut, Fig. Al); they correspond to 



* Larval eye-spots are found both in the Pterygotl and Ev.rypteri of America ; 

 see Hall's Paleontology, and also iu the carapace of the great Pterygotv.s cmglicvt 

 of England. 



f Several small Limull occur both in the coal measures of Coalbrootdale and 

 in Ireland, and it seems probable, from Mr. "W. H. Baily's observations, that their 

 abdominal segments were moveable and not fixed, as in the living King crabs. See 

 explanation of sheet 2so. 137, p. 12 — 14, Geological Survey, Ireland, 1S5!>, and 

 Annals and Mag. Natural History, 8. 3, vol. ii., pi. 5, 



