CRUSTACEA CASPIA. 297 



posterior edge is nearly straight and perfectly smooth, whereas in the pen- 

 ultimate pair it^s arched and fringed with a number of ciliated setfe. The 

 meral joint gradually widens distal ly and is obliquely truncated at the end, 

 with the anterior corner more prominent than the posterior. The carpal 

 joint is considerably smaller, and likewise obliquely truncated at the end, 

 but in an inverted manner, the posterior corner being the more prominent. 

 On tlie outer side of this joint there are 2 oblique rows of strong curved 

 spines, the lower row, terminating at the posterior corner, containing G spines 

 successively increasing in length distally. The propodal joint is very narrow, 

 sublinear, and much longer than the carpal one. The dact\lus is compara- 

 tively short and strongly curved, being more or less extended outwards, for 

 which reason it often appears inverted. Both those pairs of legs are generally 

 found to be strongly reflexed, with their outer part extended laterally (see 

 fig. 1), and it is most likely tliat they are of essential service in affixing the 

 animal within its tube. 



The last pair of pereiopoda (fig. 8) exhibit an appearance very different 

 from that in the 2 preceding pairs. They are very slender and elongated, 

 considerably exceeding half the length of the body, and are generally ex- 

 tended straight backwards. The basal joint is lamellarly expanded and 

 broadly oval in form, though somi'what tapering distally. It is fringed on 

 both edges with numerous slender plumose setie, arranged in a double row, 

 those of the anterior edge being generally curved downwards. The outer 

 joints are very narrow and increase somewhat in length, the propodal one 

 being the longest. They are clothed with fascicles of slender bristles, those 

 issuing from the end of the joints being particularly elongated. The dactylus 

 is of moderate length, somewhat curved, and terminates in a very acute 

 point. 



The branchial lamelke (see fig. 5 and 6) are simple, oblong oval in form, 

 and only present at the base of tlie 4 anterior pairs of pereiopoda. 



The incubatory lamelhe (see PI. XX, fig. 1 and 13) are present at the 

 base of all the legs, except the anterior gnathopoda and the last pair of 

 ])ereiopoda. They are narrow linguiform in shape so as not to fit together 

 with their edges. As they, however, are all round fringed with strong 

 incurved setae, the ova in the marsupial pouch are by these means securedly 

 kept in place. 



The pleopoda (PI. XX, fig. 14) are distinguished by the unusual de- 

 velopment of the basal part, which is produced inside to a very large and 

 broad, sublamiuar expansion, into which a bundle of strong muscular fibres 

 are seen to pass. Inside the obtuse tip of this expansion 2 peculiarly con- 

 structed spines are found to be secured, being placed close together and 



<I'ii3.-M;iT. CTp. 205. 25 



