1110 



CRUSTACEA. 



acute ; and when acute, the right side is usually longer than the left, 

 and sometimes inflexed or reflexed. The head is much narrower than 

 the cephalothorax. 



The eyes are situated on the anterior angles of a single spot of 

 bright red pigment, which is rather large and nearly square. 



The anterior antennse of the species observed have seventeen to 

 twenty-three joints, and they either curve as they leave the head, and 

 so bend around till the two are in one transverse line ; or they pass off 

 straight, but obliquely, then bend abruptly outwards, so as to lie in 

 one line. The tips in one species are a little forward of the general 

 line. 



The joints of these organs are short. The second is longer than 

 the first. Generally, after the second, there are four joints (3, 4, 5, 6), 

 nearly equal. Then the antennse is commonly abruptly smaller, and 

 joints 7, 8, 9, 10, 11, are small and short; 12, 13, 14, 15, 16, 17, 

 gradually increase a little in length; 18, 19 are similar to 17; 20, 21, 

 22 are a little shorter; and 23, the apical, is longer, or nearly equal to 

 21 and 22 together. Where the number of joints is less than twenty- 

 three, the order of sequence is of course different ; this reduction in 

 the number of joints arises apparently from a coalescence of some of 

 the joints following the second. 



In the right male antennse the geniculating joint precedes the sixth 

 joint from the apex, instead of the fifth, the usual place in the Pontellse. 

 The two joints next following the articulation are commonly united in 

 one, yet are sometimes separate. The two preceding the articulation 

 are one, and its apical half, or sometimes the whole, has the front 

 margin very minutely pectinate. The four joints next preceding, or 

 joints 12, 13, 14, 15, in the above enumeration, are slightly enlarged 

 and distinct. 



The setse of the antennse are not over three or four diameters of 

 the organ in length. 



The posterior antennse are two-branched. The shorter branch, as 

 in the Pontellse, terminates in more than three setse, and has no setse 

 on the outer side of the first joint. It is two-jointed, but the second 

 joint is very short. The setse at the extremity of the longer branch 

 are similar to those of the other Calanidse. 



The mandibular palpus is essentially the same as in the Calani. 

 The maxilla is three-jointed. The second joint is broad, and has a tuft 

 of setse near its base, and a long pencil at the outer angle. The third 

 joint is small, and terminates in a tuft of setse. 



