28S 



T. IWAKAWA. 



abdominal ventral plate and of the tarsal flagellum of the females, the 

 comparison of the males having been entirely overlooked. 



The first abdominal ventral plate of T. crucifer is said to be widely 

 sinuated at the hind margin and to be provided with a deep Y-shaped 

 median groove on the surface near the front edge ; while that of T/i. 

 stimpsoni should have the same margin abrupt and only slightly sinuated 

 and to be provided with a deep, quadrangular groove near the front edge 

 and on the sides of the median line with two streak-like but bent grooves, 

 which approach each other below the median groove. 



Such a difference (Pl. XI, fig, 2. A. B.) can indeed be observed on 

 the abdominal plates of crucifer and stimpsoni, but it seems to me to be 

 too slight to base specific distinction on. The Y-shaped and quadrangular 

 grooves are not fundamentally different, for the former can be easily 

 modified into the latter by supposing that the limbs of the letter Y became 

 more divergent and the notch a little deeper. I have found a quadran- 

 gular groove on the first abdominal ventral plate in one of the three 

 female specimens from the Loo-choo Islands ; but in the other two 

 individuals, which from their paler color and smaller size seem to be 

 younger females, I could not observe any indication of such a groove, but 

 only the commencement of the median and lateral grooves ; and in the 

 youngest of the three, the hind edge was rather truncated instead of being 

 sinuated (Pl. XI, fig. 2, C. D.) 



The outline and the engravings of the first abdominal ventral plate 

 seems, at least in the females, to undergo a gradual change with age, and 

 finally to reach the adult condition of sinuated shape with either a 

 Y-shaped or a quadrangular groove. 



In regard to the tarsal flagellum, which consists of nine joints in both 

 sexes, the eighth and the ninth joint are stated to be black on the lower 

 side, and to have a deep incision near the base of each joint in the female 

 of crucifer (Pl. XI, fig. 3). In that of stimpsoni they should be simply 

 cylindrical and destitute of such an incision, the fifth and the eighth joint 

 of this species being black and thicker than the rest. The characters 

 of the joints regarded to be peculiar to crucifer, I have found also in one 



