ISOMETIU'S. 



49- 



B. 



of the anterior border ; the black on the tail forms a more distinct 



network, surrounding circular or 

 oval yellow spots ; vesicle black, 

 with round yellow spots ; the 

 chelae, too, including the hands 

 and lingers, are black with round 

 yellow spots. Structural features 

 practically as in /. europcus, 

 though the brachium is a little 

 broader as compared with its 

 length, being very perceptibly 

 broader than the hand. Differing 

 from the rest of the species in 

 possessing a semicircular lobate 

 expansion at the base of the 

 shaft of the pectines, such as is 

 found in the allied American 

 genus Titjfus, where it is confined 

 to the female. 

 Measurements in mm. — Total length 34, carapace 3'8, tail 22. 

 Loc. Ceylon (Tliwaites). 



Fig. 13. — A. Base of pee ten showing 

 lobe (ft) of Isometrus thwaitesii. 



B. Tarsus and extremity of protarsus 

 of 4th leg of Isometrus europceus. 



B. 



36. Isometrus basilicus, Karsch, MT. Munch, ent. Ver. iii, p. 113, 

 1879; Simon, Ann. Mus. Genov. xx, p. 370, 1884; Kraep. Jb. 

 Hamb. Wis*. Anst. xiii, p. 127, 1890; id. Tien:, Scarp, etc. p. 68, 

 1899. 



Colour variegated yellow and black, yellow predominating; ante- 

 ocular area of carapace mostly yellow ; terga with median keel, 

 lateral border, ><-shaped marks, and a round spot on each side 

 of the middle line yellow : sterna yellow, marbled with black ; 



tail yellow, darker posteriorly, 

 slightly spotted laterally, more 

 strongly lined beneath with black, 

 vesicle slightly spotted below ; 

 chela? yellow, a few black spots 

 on humerus, brachium, and hand: 

 hand at base of immovable finger 

 black ; fingers black, with yellow 

 tips ; legs yellow, with a few black 

 spots. 



2 . Carapace granular through- 

 out, only a little shorter than the 

 1st and 2nd caudal segments and 

 quite as long as the 5th. Terga 

 granular, "like the carapace. Last 

 sternum with the median pair of 

 keels obsolete, the laterals complete. Tail Bhort, only a little more 

 than .four times as long as the carapace; 1st segmentaboul as long 

 as wide, 4th less than 5th, a little more than twice as long as w ide ; 



E 



Fig. 14. — Isometrus basilicus, tf . 



A. Vesicle and aculeus. 



B. Extremity of chela. 



