324 Mr. J. W. Salter on some new Palaozoic Star-fishes, 



moderately elongate, and formed of many rows of small spinous 

 ossicles above (with a madreporic tubercle near the angle of 

 one pair of arms) ; ambulacra deep, with transverse ossicles, 

 and a single row of large adambulacral plates. Disk plates 

 between the arms none. [Lower Silurian to Carboniferous.] 

 5 species. 



Genus 2. Palasterina, M'Coy*. Pentagonal, depressed, the 

 arms a little produced, with three or five principal rows of 

 tubercles above, combined with a plated disk which fills up the 

 angles; ambulacra rather shallow, of subquadrate or slightly 

 transverse ossicles, bordered by a single row of squarish large 

 plates, the lowest of which {ad-oral adambulacral plates, Huxley f) 

 are large and triangular, bearing combs of spines. [Upper 

 Silurian.] 



Genus 3. Palaocoma, n. g. Flat : all the centre of the disk 

 above membranous, with scattered star-like spiculse of lime, the 

 angles filled up with a similar membrane. Arms of several rows 

 of quadrate, reticular plates or ossicles, the outer ones fringed 

 with spines. Beneath, the ambulacra are narrow and very 

 shallow, the ossicles square or even elongate, and placed alter- 

 nately. Two rows of bordering plates, — the inner squarish and 

 free from spines, the outer oblique and with combs of very long 

 spines. A loosely reticular membranous web between the arms. 



Subgenus Bdellacoma [jBhlXka^ a leech). 



Arms as in Palaocoma, but elongate [and with no membranous 

 disk between them ?] ; the ambulacral ossicles much contracted 

 and with wide, open pores between. The upper surface with 

 short, scattered clavate tubercles ; margins with hair-like spines. 



We have at present only one species, but the characters are so 

 remarkable, that I cannot avoid giving it a name. If it were 

 quite certain there was no membranous web between the arms 

 (our specimens show no trace), it would clearly form a distinct 

 genus. 



Subgenus ? Rhopalocoma {poiraXov, a club) . 



Disk broad, membranous, with stellate spiculge, which become 

 square, reticular meshes upon the arms, and bear clavate, com- 



does not make quite clear the structure of the ambulacra ; they are, how- 

 ever, bordered by the large row of plates. 



* Suggested by Prof. M'Coy for this Upper Silurian Star-fish, which 

 seemed to him to differ from Uraster, and to resemble Asterina. He did 

 not, however, describe the genus. 



t Angle-ossicula (Forbes). 



