’s RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 127 
IV. — SYNOPSIS OF THE GENERA SES ARMA, METASESAR- 
MA, SARMATIUM AND CLISTOCOELOMA, WITH A KEY 
TO THE DETERMINATION OF THE INDO-PACIFIC SPECIES. 
BY Dr. J. J. TESCH. — (WITH PLATES XV, XVI AND XVII, AND 8 TEXT- 
FIGURES). | 
The genus Sesarma, established in 1817 by Say to receive an Ame- 
rican form has turned out to contain such a large number of species, that 
it is nowadays one of the most difficult ones to the systematist. No less 
than about 130 species without the subspecies are included in it. In 
dealing with so many forms the need of subdivision naturally presents 
itself, and so de Man in 1887 (Zool. Jahrb. Syst., Bd. 2) firstly distinguished 
four subgenera, to which in 1895 (Zool. Jahrb. Syst., Bd. 9) he gave the 
names of Sesarma s.s., Hpisesarma, Parasesarma and Perisesarma. But 
already two years afterwards the often tyrannic exigencies of priority in 
nomenclature induced Miss Rathbun (Proc. Biol. Soc. Washington, v. 11) 
to alter the first two names into Holometopus and Sesarma s.s. respectively, 
and in 1909 (Proc. Biol. Soc. Washington, v. 22) this author again sub- 
stituted the name Chiromantes Gistel for de Man’s Perisesarma, so that 
now only Parasesarma has been left undisturbed. 
Every carcinologist will be ready to acknowledge de Man's great 
merits in affording the most accurate and minute informations about in- 
sufficiently-known species and in describing new ones with such accuracy 
_ that we may safely follow his lead amongst the intricacies and sometimes 
bewildering complexities that present itself in Decapod literature. In the 
particular case we are now dealing with it is he, who has examined by 
far the greater number of species, at least those from Indo-Pacific origin, 
and as most of his material is represented in the Leiden Museum the 
present author has had ample occasion to test the reliability of his own 
determinations. In some doubtful cases Dr. de Man with never failing 
helpfulness has been always willing to-give his advice and needless to 
say that I again feel greatly indebted to him. 
Metasesarma, like Sarmatium and Clistocoeloma, is here treated of as 
a distinct genus. I have taken as base de Man's revision of the Indo- 
Pacific species of Sesarma (and Metasesarma) and Sarmatium that appeared 
in 1887 and prepared a list of all the species known, together with all 
their records and the synonymy. This drawing up of records has been 
the most tedious part of my task in the present paper and I feel sure 
that, notwithstanding all my trouble, some records have been fortuitously 
