some undescribed exotic Crustacea. 195 



when it becomes luminous. It was found in great numbers in calm 

 weather oiF the southern peninsula of Africa. 



Fig. 8. a, Tlie animal magnified. 



Calanus (Leach) Arietis. Plate XXI. fig. 9. 



Pearly blue, purplish interiorly. Elongate-ovate, narrowed slightly 

 anteriorly. Head small, quadrate, seemingly formed of a central 

 part containing a deeply immersed rufous eye, and two lateral parts 

 forming the roots of two extremely large antennae. Antennae curved, 

 multiarticulate, spiny, the penultimate and preceding joint being 

 furnished with two rather long spine-like processes directed back- 

 wards, and carrying numerous acute ciliae, which, as in Beroe and 

 Cestus, are perpetually in motion, throwing out iridescent tints. 

 Behind the head the body is irregularly tumid, and gives origin be- 

 neath to three pairs of robust, somewhat clavate legs, carrying nu- 

 merous long waved spines or hairs. The fin-legs could not be ob- 

 served, from the minuteness of the animal rendering vision obscure; 

 they seemed however pretty numerous. The last segment of the 

 body was concave posteriorly, and supported the tail, which was 

 about half the length of the body, and dilated posteriorly, the seg- 

 ments having on each side an obtuse process descending and covering 

 the articulation with the next segment laterally. The last joint had 

 on each side a quadrangular appendage, with long curved spines, 

 and internally a valvular part was observed to expand and contract 

 with extreme regularity, like the dorsal vessel of some insects. 



This minute species, which unquestionably belongs to the genus 

 Calanus of Leach, was detected in the middle of the Atlantic Ocean. 

 The- ciliaj at the extremities of the antennae are extremely curious, 

 and I believe not to be found in other species of the same genus ; but 

 I have not lately had an opportunity of examining G. longicornis, 

 from which this differs in many other respects. 



Fig. 9. a, Calanus Arietis, magnified. 



h, Portion of one of the ciliated spines. 



c, The form of the posterior edge of the caudal segments. 



d, The anterior leg, in one specimen. 



Cyclops ? (Midler) laticauda. Plate XXI. fig. 10. 



Hyaline ; the eyes, which are separate, and minute dots along the 

 dorsal plates rufous. Head very large. Antennae very short and 

 spiny, three irregular joints only, projecting beyond the head ; first 

 segment of the body as broad as the head, rest diminishing in width, 

 last angulate posteriorly ; first and second caudal segments smaller 

 than the third, which is nearly semicircular in outline ; three poste- 



