98 DESCRIPTION OF THE HAED PARTS OF SOME 



actinal limestone network. The small size of the first set of ambulacral 

 plates is characteristic of the genus as well as of other Starfishes with 

 two rows of suckers ; the plates of the actinal are scarcely more promi- 

 nent than the other ambulacral and interambulacral plates, forming a strik- 

 ing contrast to the immense development they take in Asteracanthion 

 and allied genera. The interambulacral plates, as is well shown on PI. X. 

 F'kj. 5, are remarkably uniform in size ; the secondary ambulacral plates 

 forming the brachial limestone network adjoining them are compactly 

 soldered together. In this genus the spines of the limestone network 

 are completely sheathed by the outer membrane covering the whole abac- 

 tinal and actinal system (PI. X. Figs. 1, 2) ; they are large, sharply pointed, 

 generally placed only at the angles of the limestone polygons, and form 

 irregular longitudinal rows, from the central part of the abactinal part 

 of the disk, gradually diminishing in size towards the extremity of the 

 arms. This species is particularly abundant in the West Indies and Florida, 

 and extends northward to New Jersey. 



CROSSASTER. 



Crossaster M. T. 1840, Monatsl). d. Akad. Berlin, (emend.) A. Ac. 



The genus Crossaster, as originally established by Muller and Troschel 

 in the Monatsbericht d. Akad. d. Wiss. of Berlin, was identical with So- 

 laster of Forbes, which had the priority of a year. In the System d. Asteri- 

 den, Miiller and Troschel adopted Forbes's genus. From an examination 

 of the hard parts, it is evident that Solaster papposus and Solaster endeca 

 should not be included in the same genus, having really nothing in com- 

 mon beyond the great number of arms. The accompanying descriptions 

 Avill fully show my reasons for placing these two species in different gen- 

 era. In order not to multiply names, I have retained the genus Cros- 

 saster, which is quite closely related to Pycnopodia, only limiting it to S. 

 papposus, and have kept Solaster for S. endeca and its allies, which are 

 more nearly related to Cribrclla. 



