of the Division Hyperina. 3 



carpus is considerably more produced, reaching nearly to the 

 extremity of the propodos ; the propodos is long, having the 

 anterior surface concave, and the infero-distal angles on each side 

 produced to a point ; dactylos half the length of the propodos, 

 and terminating in a curved unguis capable of shutting into the 

 concave surface of the propodos. The fifth pair are rudimen- 

 tary, the last joint terminating subapically in an unguiculate 

 spine. The pleopoda are but imperfectly developed, two or three 

 pairs only being present, and these consisting of a peduncle and 

 two inarticulate rami, which probably are those of the three an- 

 terior pairs. The telson is as broad at the base as the preceding 

 segments, and terminates obtusely. 



The earliest and latest stages of this creature offer a con- 

 siderable degree of variation in some points. The form of the 

 cephalon differs : in the adult it is truncate in front, oblique 

 beneath; in the young the dorsal surface gradually declines 

 to the anterior margin, which is on a line with the inferior sur- 

 face of the cephalon. The superior antennse in the adult consist 

 of a peduncle of three short joints, and a long, broad, flat, in- 

 ternally concave, uniarticulate flagellum, and are situated in 

 the frontal surface of the cephalon ; in the young they consist 

 of six joints, decreasing gradually in length and breadth to the 

 extremity, where they are tipped with four small stiff hairs ; they 

 are situated at the anterior extremity of the cephalon. The 

 inferior antennae in the parent are six- or seven-jointed, while in 

 the young animal they are almost obsolete, consisting of a 

 single joint of small dimensions tipped with two hairs. In the 

 adult we find the gnathopoda strong, well-developed, and efficient 

 grasping organs ; in the young they still retain an embryonic 

 condition, and exhibit none of the characteristics peculiar to 

 their future form. The first two pairs of pereiopoda bear a 

 strong relative resemblance to one another, those of the young 

 differing but little from those of the parent. The two suc- 

 ceeding pairs in the adult are long, and evidently formed for 

 seizing upon certain substances and securing itself in position, 

 while those of the young are not longer than those of the pre- 

 ceding pair ; they are also capable of holding certain substances ; 

 but while they possess this power in common with the adult 

 animal, the plan by which it is attained differs considerably. In 

 the adult the long slender propodos has the anterior margin 

 minutely serrated, and is capable of being bent against the an- 

 terior margin of the meros and carpus ; and, to make the grasp 

 more secure, it impinges between two short spines at the distal 

 extremity of the carpus. In the young, the two pairs are not 

 exactly uniform ; they agree in character, but differ in degree and, 

 perhaps, in power : in the fourth pair, the carpus has the anterior 



1* 



