242 ON THE GENUS NOTOPYGOS. 
an erroneous diagnosis of the genus Notopygos and proposed 
the new name Lirione for two species, undoubtedly belonging 
to the first named genus, that of Grube. Baird ') did not 
recognize this error, that was corrected by subsequent inves- 
tigators (Ehlers, MacIntosh a.o.). Nowadays about a dozen 
of species of Notopygos are described, but, as is rightly 
stated by Potts*), they are unfortunately rather ill-defined 
and so it is sometimes a very difficult, if not an impossible 
task to recognize the species. Potts found that one or more 
of the anterior segments always possess denticulated setae, 
even when in an other region of the body they are not 
present. I for one think however, that the presence or 
absence of serrations in the setae is not the only character 
that must be taken into account, as, like in Chloeta, the 
branchiae do not seem to commence always on the same 
segment and also the number of the folds of the caruncle 
and the situation of the anal pore differs in different species, 
though unfortunately in several cases this is not mentioned 
by the authors. In the following table the hitherto des- 
cribed species of Notopygos are enumerated, especially in 
order to demonstrate the numerous gaps in our knowledge 
of this genus. 
NOTOPYGOS. 
A. Branchiae commencing on the 4th segment. 
1. ornatus Gr. loc. cit. Puntarenas (Costa Rica). 
B. Branchiae commencing on the 5th segment. 
a. Anus situated on segment 21 (Ehlers), intersegm. 
groove 21/22 (Grube). 
2. crinitus Gr. loc. cit. St. Helena, Florida, Portorico. 
b. Anus situated on segment 22 (Baird), 23 (Horst). 
3. Rayneri Baird, loc. cit. p. 226, pl. IV, fig. 6, a,b. 
North-east coast of Australia. 
1) Journal of the Linnean Society, Zoology, Vol. X, 1870, p. 226. 
2) Trans. of the Linnean Society, Zoology, (2) Vol. XII, 1907/09, p. 358. 
Notopygos ornatus Gr., N. (Lirione) Rayneri Baird and N. (Lirione) splendens 
Kinb. have been overlooked by this author. 
Notes from the Leyden Museum, Vol. XX XIII. 
