XVIH INTRODUCTION. 



the second pair (Fig. vi., 5) of two plates with numerous hairs at 

 their extremities. The maxillipedes (Fig. vi., 6) are broad and 

 foliaceous the basos and ischium being produced internally into 

 lamellar expansions. Behind the mouth is a lower lip, labium or 

 metastoma. The following two pairs of appendages belonging 

 to the two first distinct thoracic appendages are formed on the 

 same plan, and are called the gnathopoda (Fig. v., and Fig. vi., 

 7 and 8) ; like the legs of the Prawn and the Crab, each of these 

 consists of seventeen joints ; the first or coxa is expanded and 

 plate-like ; the basos is long and narrow ; the ischium, meros 

 and carpus short ; the pi*opodos much larger in the posterior 

 than in the anterior pair, and with the dactylos forming a 

 subchelate hand, the dactylos shutting backwards against a lower 

 or distal palmar border of the propodos so as to constitute an 

 organ of prehension. The two following pairs of appendages 

 (pereiopoda) (Fig. v., 9 and 10) resemble the gnathopoda, except 

 that the propodos and dactylos do not form a subchelate hand, 

 and like them are turned forwards. The remaining three pairs 

 of thoracic appendages (posterior pereiopoda) (11, 12, 13) 

 resemble in general form the anterior pereiopoda, but are turned 

 backwards. 



The appendages of the abdomen fpleopodaj consist of six 

 pairs. The first three (Fig. v., 11, Fig. vi., 15) pairs consist of a 

 basal protopodite with a pair of equal, foliaceous, many-jointed 

 rami., much like the abdominal swimmerets in the Prawn. The 

 fourth and fifth pairs (Fig. v., 17 and 18) have the rami styliform 

 and one-jointed ; the last pair (19) are very small in the Sand- 

 hopper. Finally, the telson of the Sand-hopper is small, being 

 represented only by a blunt conical elevation. The branchioa of 

 the allies of the Sand-hopper consist of delicate sacs, one 

 attached to the coxa of each of the second pair of gnathopoda, 

 and of each of the pereiopoda. In the female delicate 

 membranous plates (oosi elites ), serving as a protective covering 

 to the eggs, are attached above and internal to the first four 

 pairs of branchiae. 



The alimentary canal presents, as in the Prawn, a gastric 

 dilation situated in the head, and possessing an armature of 

 calcareous pieces and of teeth. A small coecal diverticulum 

 the cervical gland is given off from the intestine immediately 

 behind the stomach. The liver is in the form of tubes lined 



