the Crustacean Genus Thaumastocheles. 231 



Museum of University of St. Andrews, "Off Yenoshima, 

 Odawara Bay, Japan, 200 fathoms, July 1898, Mr. W. 

 Balsillie." Length of carapace and rostrum 62 mm. ; of 

 larger chela 118 mm. ; of smaller chela 56 mm. This 

 specimen is the largest yet recorded in the genus. 



The spines on the antero-lateral regions of the carapace are 

 more numerous than in Th. zaleucus. The raised line which 

 marks the anterior margin of the carapace shows on each 

 side of the base of the rostrum an orbital bay, which, how- 

 ever, is smaller and more concealed by overlying fur than in 

 the type of Th. zaleucus. The rostrum is turned upwards at 

 the tip, not downwards as in Doflein's specimen, and there 

 are about five pairs of marginal spinules concealed in the 

 shaggy fur that covers it. The dorso-lateral ridges of the 

 abdomen, which in Th. zaleucus are dentate or tuberculate on 

 all the somites, are so here only on the first three, becoming 

 low and smooth on the last three somites. 



The arrangement of the teeth on the fingers of the larger 

 cheliped requires further description. In Th. zaleucus (fig. I.) 

 the teeth are set in a single row — that is to say, with their 

 bases in line — for the greater part of the length of the fingers, 

 but they slope alternately to either side of the plane in which 

 the two fingers lie, so as to form two rows at an angle of 

 about 30° with each other. Towards the proximal end of 

 the fingers the bases of the two rows begin to move apart, 

 and the arrangement becomes truly biserial. Throughout 

 the greater part of each row large and small teeth alternate 

 in regular order, so that the periodic arrangement, taking 

 both rows together, may be represented by the formula 

 A ABB A. 



In Th. jajionicus (fig. II.), on the other hand, the teeth are 

 in a single row, and all lie in the plane of the fingers ; they 

 are of four orders of size, and are arranged with beautiful 

 regularity (which only becomes disturbed towards the base 

 and tip of each finger) in periodic sequence agreeing with 

 that observed by Stahr * and by Herrick f in the chelae of 

 the lobster. The sequence may be represented by the formula 

 ADCDBDODA, At the proximal end of the immovable 

 finger is a single tooth set out of the line of the others and 

 pointing obliquely towards the side that is ventral when the 

 chela is extended. This tooth apparently corresponds to one 



* Jenaische Zeitschr. xxxiii. 1898, p. -!■". 



t Bull. Bureau fisheries, Washington, xxix. 1009, p. 260 



