;Q30 CRUSTACEA. 



individuals of a species may occur colourless, while others are deeply 

 coloured. Some deep green and yellowish species were observed; 

 also, a few reddish, or pale umber. Several have a silvery, or pearly 

 white back, which presents a bright appearance in the water. One 

 yellowish individual was crossed by an elegant crimson band of great 

 breadth, presenting a beautiful effect. The blue species commonly 

 have the alimentary canal green or greenish, which shows through 

 along the middle of the cephalo thorax ; in a few species it has a 

 brownish colour. 



In some instances, the tips or bases of the anterior antennae, the 

 bases of the caudal setae, and some other organs are coloured. 



Size. — The adult Pontellae usually vary in size, from one line to 

 half a line. There are many species as long as an eighth of an inch, 

 and a single one was found which measured one quarter of an inch in 

 length. The length, as here given, includes the distance from the 

 beak to the extremity of the abdomen, exclusive of the caudal stylets; 

 and this is always our use of the term in the descriptions following. 

 The common proportions between the length and breadth of the 

 cephalothorax, is as 3 to 1. There are slender species with the ratio 

 4 to 1, and stout species with the ratio 2 to 1 and It to 1. The 

 abdomen is common \y one-third to one-fourth the length of the cepha- 

 lothorax, and never exceeds or hardly equals one-half its length. 



Habitat. — The species of Pontellae are widely distributed through 

 the oceans. The hand-net was seldom used without bringing up some 

 individuals, especially when the time just before daylight was devoted 

 to this kind of fishing. In these respects, and also, in their greater 

 abundance near the surface in calm weather, they are like the Calani. 

 They are, however, much less common than the Calani in the higher 

 latitudes, being mostly confined to the seas between the parallels of 

 30° either side of the equator. 



The specimens often have the setae of the antennae and caudal sty- 

 lets mutilated, especially the latter. In some instances, not more 

 than one specimen in thirty had the caudal setae entire. Sometimes 

 all the setae of the antennae are broken off* and give a false character 

 to these organs, calculated to lead to error in description. 



Affinities. — The relations of the Pontellae to the Calani have been 



