on the Genus Solaster. A437 
others, for example Viguier and Perrier, will not accept any 
division, and have therefore retained Forbes’s original generic 
name. 
Prof. Verrill has established a new genus, Lophaster, for a 
third species, namely Solaster furcifer, which some few natu- 
ralists are inclined to accept. Thus for three species of the 
original genus Solaster, which is so poor in species, three 
genera, Lophaster, Crossaster, and Solaster, have been formed ; 
and these we now propose to submit to a critical examination. 
Prof. A. Agassiz, who first set up Solaster papposus as the 
type of a new genus and named it Crossaster, which is 
Miiller and Troschel’s first name for it *, expresses himself as 
follows in hismemoir on North-American starfishest :—‘* From 
an examination of the hard parts it is evident that Solaster 
papposus and S. endeca should not be included in the same 
genus, having really nothing i common beyond the great 
number of arms. ‘The accompanying descriptions will fully 
show my reasons for placing these two species in different 
genera.” In his descriptions of Solaster papposus and endeca 
we cannot find any such great differences as would justify 
their separation into two genera; and in this respect we must 
agree with Dr. Viguier that it is rather difficult to understand 
why this distinction is made. 
Prof. Agassiz himself says, in his important work just 
mentioned (p. 112) :—“ In Solaster endeca the arrangement 
and general structure of the ambulacral and interambulacral 
plates are identical with those of Crossaster. . . . ‘The funda- 
mental difference between the genera Crossaster and Solaster 
lies in the structure of the abactinal floor. The actinal floor 
between the arms is composed of small somewhat elongated 
plates, arranged in more or less irregularly diverging rows, 
quite similar to those of Crossaster.” 
According to what is here stated, it is principally the dermal 
skeleton of the back upon which Agassiz lays so great stress 
that he allows it to be decisive of the division of the genus. 
Dr. Viguier, in his memoir on the skeleton of the Asteridat, 
has pretty clearly shown that the dermal skeleton in Solaster 
papposus does not differ from that of S. endeca in any so 
essential degree as to render necessary any division of the 
* In the ‘System der Asteriden’ of Miller and Troschel, however, 
Forbes’s generic name Solaster is adopted for papposus, and Crossaster is 
cited as a synonym. 
qi Momoue of the Museum of Comparative Zoology at Harvard Col- 
lege, vol. v. no. 1, p. 98 (Cambridge, 1877). 
ft “ Anatomie comparée du squelette des Stellérides,” par le Dr. Vi- 
guier, Archiyes de Zoologie expérimentale et générale, tome vii. p. 138 
(1878). 
