50 Dr. F. A. Bather — Studies in Edrioasteroidea. 



at the broken edges of the plates the clean crystalline cleavage 

 distinctive of calcite and of echinoderm stereom, hut not found in 

 fossil remains of Arthropoda. Their echinoderm nature once recog- 

 nised, it is further clear that all these fossils represent the stems or 

 turrets of species resembling those from Minnesota and Girvan so far 

 as that portion of the anatomy is concerned, and probably resembling 

 them in the structure of the oral face. It is interesting to note that 

 among the Gotland fossils referred by Aurivillius to Scalpellum sul- 

 catum, is one which Hisinger had previously figured as " Column S3 

 Crinoidis fragmentum " (1841, Lethcea Suecica, Supplementi Secundi 

 Continuatio, pi. xli, fig. 6). This reference by Hisinger, which, 

 bearing in mind the former extended connotation of the name 

 Crinoidea, now proves perfectly correct, seems to have aroused no 

 suspicions in the mind of Aurivillius. On the contrary, he was quite 

 certain that these fossils represented tbe stems of some genus of 

 Lepadidse, and, despite the great extension of geological range involved 

 and the absence of congeners earlier than Cretaceous, he scarcely 

 hesitated to refer them to the characteristically recent genus 

 Scalpellum. 



Students of early Palaeozoic fossils know how often it has proved 

 difficult to decide whether isolated plates, or associated fragments, 

 or even whole skeletons, belonged to the Echinoderma or to the 

 Arthropoda; but the criterion of stereom -structure, when it can be 

 applied, ought to prove decisive. Apart from that, in the present 

 instance, Aurivillius himself notes that in the peduncles of Recent 

 Cirripedia the scales are embedded in a thick [uncalcified] chitin, or 

 are only fastened by the base. In other words, the peduncle-valves 

 of the cirripedes are never so closely set or so deeply imbricate as are 

 the plates in these Silurian fossils ; and the consequence of this is 

 that up to the present, as Mr.Witbers assures me, only two specimens 

 are known in which a scalpelliform peduncle has been preserved in 

 the fossil state with its valves in place, 1 and not a single one has 

 been found apart from its capitulum. What a contrast is provided 

 by the fossils before us, of which over a score have been picked up on 

 a single beach in Gotland and fourteen in one Shropshire lane ! 



But apart from these fairly obvious considerations, which would 

 have made an ordinary palaeontologist hesitate, the general shape of 

 the individual plates might well have raised a doubt in the mind of so 

 high an authority on the recent Crustacea as Professor Aurivillius. 

 The peduncular valves of cirripedes always show growth-lines over 

 the whole outer surface, and definite facets where they abut or over- 

 lap ; they are clear-cut structures, and in Scalpellum at any rate the 

 earlier the species the more characteristic is the shape of the plate. 

 But the plates of these Wenlockian fossils show at the most some 

 minute irregular granules or rugse, and have no distinct ridges or 

 facets ; they are quite unlike any cirripede plates of either Silurian or 

 Becent times. 



1 Scillcelepas carinata (Phil.), Miocene, Sicily : Seguenza, 1876, Atti 

 Accad. Pontaniana, vol. x, pi. viii, fig. 14 ; and Pollicipes concinnus Morris, 

 Oxford Clay, England : Darwin, 1851, Pal. Soc. Monogr. Foss. Lepadidse, 

 p. 50, pi. iii, fig. 1. 



