Mr. J. W. Salter on some new Palmzoic Star-fishes. 333 



widely, both in specific and generic character, from all that are 

 yet described. 



P.ferox. PL IX. fig. 6. 



P. disco magno, e squamis hexagonis majoribus spiniferis struct© ; 



assulis (brachialibus sen) ambulacralibus intra discum creberrimis ; 



ossiculis oris robustis parallelis. 



We have only the disk, and its angles are not complete. It 

 is composed of large, irregularly rhomboid plates, radiating in 

 seven or eight rows from the mouth in each interambulacral 

 space, and furuished with short spines. 



The inner angles of each of these spaces form a prominent 

 triangular boss or tubercle, cut off" distinctly by a furrow, and 

 between these are the large elongated basal plates {b) of the am- 

 bulacra, lying parallel, and not at all divergent. They are thick 

 and blunt, and, together with the bosses above mentioned, form 

 a circumscribed star in the centre, the massive character of 

 which contrasts strikingly with the thinness and delicacy of all 

 the other parts either of the ambulacra or disk. The ambulacra 

 are narrow, composed of a double row of transverse plates,, nar- 

 rower and more crowded than in Palasterina or Palceaster, and 

 apparently very thin in texture. They can be detached, and 

 leave the upper plated surface (a) free, which is covered with the 

 irregular plates. If there be no deception in this — for we have 

 only a single specimen — the affinity would be much closer with 

 the forms above mentioned, although the strong oral apparatus 

 reminds us more nearly of the Protaster. Till other specimens 

 are obtained with the angles perfect, it will not be easy to decide 

 whether it be an Ophiurid with contracted arm-plates, or one of 

 the Asteriadse with a greatly developed masticatory apparatus. 

 The powerful teeth suggest the specific name. The specimen is 

 in the cabinet of Mr. Marston of Ludlow, who has contributed 

 largely to the illustration of these Silurian star-fish. 

 Loc. Leintwardine, 



Other species, both of Protaster and of Palaocoma, are known, 

 but it is only necessary here to notice those which serve to illus- 

 trate the genera proposed in the Reports of the British Associa- 

 tion for 1856, p. 76, Trans. Sections. There are, no doubt, many 

 species yet to be discovered in the old rocks of our own country, 

 and, judging from what has already been collected, a great 

 variety of forms may be expected to reward research. 



EXPLANATION OF PLATE IX. 



[The figures are only diagrams, but express the principal characters of the 



species represented.] 

 Fig, \. Palceaster asperrimus, n. &]:>. Lower Silurian. Welchpool, North 

 Wales : a, magnified underside ; b, section of arm. 



