's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 191 



1897. M. pacificits Ortmann. Zool. Jalirb. Abt. Syst., Bnd. 10 p. 342 (no 



new record). 

 1902. „ bicarinatus de Man. Abhandl. Senckenb. Gesellsch., Bnd. 25, p. 496 



(no new record). 

 nee 1910. M. pacifions Rathbun. Buil. Mus. comp. Zool. Harvard Coll., 



Cambridge, Mass., v. 52 p. 307, pi. 1 f. 3 (= M. crinitus Rathbun). 



Unfortunately there is some confusion in the right interpretation of 

 Dana's species, owing to the fact that the figure of this author seems to 

 be incomplete, and that Heller's M. bicarinatus is not wholly reliable 

 with respect to the form of the lateral teeth of the carapace. 



De Man in 1890 first determined the very specimens of the Leiden 

 Museum as M. pacificus, later, in 1902, however, he changed his opinion, 

 and regarded these specimens as the true M. bicarinatus, whereas another 

 specimen collected by Prof. Kükenthal at Halmaheira, was referred by 

 de Man to M. pacificus. 



Miss Rathbun recently (1913) supposed, that this latter specimen of 

 de Man belonged to a new species created by her, M. crinitus, that the 

 Leiden Museum specimens ought to be referred to M. pacificus, as de 

 Man had formerly done (1890) and that If. bicarinatus „is too unlike the 

 species under consideration to be united with either" (Proc. U. S. Nat. 

 Mus., v. 44, p. 619). 



Unless the type-specimen of Heller be examined again, this question 

 must remain undecided, but I think it the safest way to suppose that 

 M. pacificus and M. bicarinatus are really identical and for the rest to 

 agree with Miss Rathbun's opinion in referring de Man's Halmaheira 

 specimen to M. crinitus. 



The Leiden Museum specimens have been so amply described by de 

 Man in 1890, that it is useless to give a fresh description here. The 

 carapace, smooth and glossy to the naked eye, is nearly equilateral, its 

 greatest breadth (which is lying between the postero-lateral teeth, so 

 that the carapace is narrowed anteriorly) being to the length as 7:5. 

 The external orbital angle is not at all pointed, but rectangular, and 

 separated from the next lateral tooth by a distinct incision. On the 

 branchial regions there are two longitudinal, slightly pubescent lines on 

 each side, a third row is lying before them and running in a transverse 

 direction, and finally there is a similar, but very short and concave line 

 just above the insertion of the posterior legs. This arrangement recalls 

 one strongly to that found in species as M. japonicus and M. tomentosus ; 

 and it is chiefly on account of the fact, that these lines are not repre- 

 sented in Dana's figure of M. paclficus, that the confusion above alluded 



