600 THE VOYAGE OF H.M.S. CHALLENGER. 



eight smaller ones, of which the anterior four or five form a small serrature ; the lower 

 margin is armed with three teeth. Pleon having the third somite dorsally arcuate, and 

 only slightly produced posteriorly in the median line and not elevated into a tooth. 



Spirontocaris spinus, var. e (PI. CVI. figs. 4, 5, 6). 



Carapace dorsally carinated and armed with five large teeth that commence about 

 halfway between the orbital and posterior margins, and the rostrum with several smaller 

 teeth, of which the anterior four form an abruptly descending serrature posterior to 

 the sharp apex ; the lower margin is armed with four teeth. The upper of the 

 supraorbital teeth is larger than the lower. 



The antennal tooth as well as that at the frontodateral angle is moderately produced. 

 Pleon having the third somite arcuate, posteriorly produced in the median line, but not 

 elevated to a tooth. 



Spirontocaris spinus, var. £ (PI. CVI. fig. 7). 



Carapace slightly carinated and elevated on the dorsum as well as on the 

 rostrum, armed with fourteen teeth of equal proportions, the anterior being the 

 smallest ; under margin armed with six of equal size ; supraorbital teeth well defined 

 but small, as are also the antennal and frontodateral teeth. Pleon having the third 

 somite arcuate and posteriorly produced in the median line, but not elevated to a 

 tooth. 



Spirontocaris spinus, var. rj (PI. CVI. fig. 8). 



Carapace anteriorly carinated and armed with six or seven large teeth, the posterior 

 four of which are smooth, the two anterior serrate, which character of teeth is persistent 

 to the apex of the rostrum. Under margin armed with three smooth teeth. Supra- 

 orbital teeth large. 



The variety S (PI. CVII.) is the nearest approach in this collection to the form of the 

 type. 



The carina on the dorsal surface of the carapace commences on the cardiac region, and 

 is furnished with five strong teeth, of which the most anterior is on a level with the 

 orbital margin ; beyond this point the rostrum is furnished with seven teeth, gradually 

 decreasing in size anteriorly, the last four form an oblique serrature terminating within the 

 extremity of the rostrum, which is produced to a strong, oblique, upwardly directed, rounded, 

 sharp tooth, which is continued posteriorly as a ridge on each side of the rostrum to the 

 orbital margin, where it is supported by two small teeth, one above the other. The lower 



