igi8.] R. B. S. Sewell : New species of Copepoda. ly 



proximal end of exopod i. On the right side, exopod i is a stout 

 segment bearing a single seta on its external margin; exopod 2 

 bears a rounded prominence on its inner aspect about the middle 

 of its length, from the summit of which a seta arises; exopod 3 is 

 curved, tapering to a point and bears a single seta on its inner 

 border. 



On the left side exopod i bears on its inner margin distally a 

 single small spiniform process ; exopod 2 bears a single small 

 marginal spine distally ; exopod 3 bears a small spine on its outer 

 border, on the inner margin is a single small seta, and terminally 

 are three unequal spines. 



The original species of the genus Acartiella, A. tortaniformis 

 (Sewell) was discovered in a collection from the Rangoon River 

 Estuary (vSewell, 1912, p. 346), and all these new species occur in 

 similar localities where the water is brackish: it is interesting 

 to note the association of Pseudodiaptomus hinghami, Sewell, with 

 Acartiella major and minor in the Chilka I.ake collection, for 

 the only other locality in which P. hinghami has hitherto been 

 found is the above-mentioned Rangoon River Estuary. 



The only truly marine form in this genus is Acartiella kempi, 

 Sewell, which occurs in the Gulf of Mannar, and it is exceedingly 

 interesting to note that this species in some respects tends to 

 approximate to species both of the genus Tortanus, a purely marine 

 genus, and of the genus Acartia in which many of the species are 

 truly marine : thus in all other members of the genus the -2nd 

 antenna has the peculiar flattened form which I described and 

 figured originally in my description of A. tortaniformis {Acartia 

 tortaniformis, Sewell, 1912, p. 346 and pi. xxi, fig. 4), but in Acar- 

 tiella kempi it presents the form commonly found in species of the 

 genera Acartia and Tortanus; again the 5th pair of legs in A. kempi 

 rf i-3 different in form from the corresponding appendage of other 

 members of the genus in that it possesses a long process on the 

 segment exopod i of the right ieg^ and further there is no process 

 on the basal joint of the same leg, a condition that approximates 

 to that found in the genus Tortanus : as regards the length of 

 the abdomen Acartiella kempi 2 nearly approximates to the genus 

 Acartia. The known forms of this genus form a distinct series in 

 respect of the proportional length of cephalo-thorax and abdomen, 

 and I give the varying proportions below together with the propor- 

 tion in two species of Acartia :■ — 



$ Species. Cephalo-thorax. Abdomen 



Acartiella tortajtif or mis .. i"5 I'O 



2'0 I"0 



Acartiella gravely i .. I'j 10 



Acartiella major} 



Acartiella minor S 



Acartiella kempi . . 2 '5 10 



Acartia chilkaensis .. 2*85 i"o 



Acartia southwelli . . 35 1*0 



