392 Dr. Strahl on the Systematic Position of the Thalassinz. 
distinct genera from Astacus: these in various ways constituted: 
a transition from the genus Astacus to the Thalassine. The 
union of the Astacine and Thalassine has been approved of by 
some naturalists, for example by Gerstiicker in his Carcinological 
Contributions in Wiegmann’s ‘Archiv’ for 1856 ; but it has been 
rejected by Dana in his great work on the Crustacea. Dana 
has united the Astacide with the Scyllaride and Palinuride, 
whilst Milne-Edwards has placed the Thalassine between them. 
In fact, however, the Astacide have much less affinity to the 
Scyllaride and Palinuride than to the Thalassine. The want of 
the antennal scale does not sharply divide the Astacide from the 
Thalassine, masmuch as there are Thalassine which exhibit traces 
of this organ, although but insignificant ones. Of Thalassine 
which possess a more or less perfect antennal scale, there are, 
besides Glaucothoé (Milne-Edwards) and Azius (Leach), also 
Calocaris (Bell) and even, notwithstanding the express denial 
of Milne-Edwards, probably the genus Callianassa—at least 
Callianassa subterranea (Leach) and C. mucronata (mihi) and 
Thalassina scorpionoides. In the atlas to Cuvier’s ‘Régne Animal,’ 
pl. 48, Milne-Edwards has given a figure of Callianassa, and in 
the further details of the organization has even perfectly and 
accurately represented the external antenne ; but as he had not 
recognized the more delicate details, the figure is deficient in 
this respect. The Scyllaride and Palinuride never have an 
antennal scale, and this alone would separate them more sharply 
than the Thalassine from the Astacide sensu stricto. But, 
in respect to the outer antenne, the Scyllaride and Palinuride 
exhibit a character which is perfectly foreign not only to the 
Astacide, but also to the Caride, Peneide, &c. In them, 
namely, the elsewhere: moveably articulated piece, which bears 
the tubercle and the perforated tympanic membrane contained 
in it, is imtimately anchylosed to the epistomium: on account 
of this anatomical character, they must form a separate sec- 
tion of the Tubercular Decapods, repeating in a certain de- 
gree the Oxyrhynchid type of the Opercular Decapods. This 
anchylosis appears to occur very early; for, from the numerous 
observations of Coste and Couch, it is now scarcely doubtful 
that the Phyllosomata, still retained by Milne-Edwards as a 
peculiar genus, are the early stages of the Palinuri. The Zoo- 
logical Museum. of Berlin possesses a series of Phyllosomata, 
about sixteen in number, taken by M. Jagor in one sweep of the 
towing-net, in the open sea near Trinidad; these show such 
gradual changes in course of growth that thirteen of them may 
be arranged in such a manner as to demonstrate the increasing 
size and simultaneous alteration of the characters most evidently. 
As, however, these are remarkable in other respects likewise, I 
