296 MARINE INVERTEBRATES 



On the cephalothorax are seven pairs of appendages. The first pair are 

 small and lie in front of the mouth ; these and the four following pairs have 

 chelae, or claws. The sixth pair have no chelae, but at the base have a pecu- 

 liar process termed the flabellum. These six pairs of appendages surround 

 the mouth, and have bristles at the base which serve as jaws. The sev- 

 enth pair of thoracic appendages are broad plates called the operculum, 

 which meet and cover the abdominal appendages to a certain extent. 

 The abdomen has five pairs of appendages, which are plate-like and re- 

 semble the operculum in form and have an upper and an under piece. 

 On the posterior surfaces of the abdominal feet are large, leaf-like folds, 

 which are the gills. In front of the first pair of thoracic legs is a small 

 tubercle supposed to have an olfactory function. Limulus has a blood- 

 vascular system (the blood being bluish in color), a nervous and a diges- 

 tive system. It walks with the thoracic feet and swims with the abdom- 

 inal ones. It enters the sand by pushing in the rounded, anterior end. 

 In moulting the carapace opens on the front edge. Limulus is edible, its 

 meat being, it is said, as good as that of the lobster. (Plate LXIV.) 



CLASS PANTOPODA (Lang) 



OEDER PYCffOGONIDA 



This order of animals, like Limulus, has no definitely deter- 

 mined position in the classification of marine organisms. About 

 one hundred and fifty species of Pycnogonida have been described, 

 of which thirty are found on our coast and are commonly known 

 as sea-spiders. They are found crawling slowly over seaweeds, 

 hydroids, and sponges, and appear to be all legs, but, like other 

 animals, have a digestive, a circulatory, and a nervous system. 

 They are devoid of organs of respiration. The body has a 

 cephalothorax, which bears a conical suctorial proboscis on the 

 anterior end, and on top a prominence containing four eyes. It 

 has three pairs of appendages, two pairs of which are sometimes 

 lacking ; then come three free segments and a rudimentary abdo- 

 men. There is a pair of short appendages bearing claws (chelae) 

 and four pairs of long walking-legs. The walking-legs contain 

 a tubular outgrowth of the body, into which the stomach extends. 

 The egg-sacs are in the legs, and open at the basal joints. The 

 male is provided with an extra pair of legs, for the purpose of 

 carrying the eggs after they are deposited by the female. The 



