SCHIZODUS AXINIFORMIS. 219 



cit.). But prior even to this, and as early as 1838, Mr. W. Rhine! had figured the 

 shell, from specimens obtained at Woodhall, as Axinus Pentlandicus, and it is 

 therefore a pity that Mr. Etheridge did not preserve the earliest specific name. 

 Though there is no description there is little doubt as to the identity of Rhind's 

 shells, as the locality is given ; and though Etheridge doubts whether the two 

 specimens figured by Rhind are of the same species, I am of opinion that they are, 

 because I have seen numerous examples which appear as in the drawings, in 

 neither of which is the correct outline of the shell shown, because specimens were 

 evidently figured which were not perfectly free from the matrix. 



Etheridge makes the following remarks on one of Rhind's types (op. supra 

 cit., p. 432), " One of these (fig. b) was afterwards refigured and described 

 by Capt. T. Brown as Pachyodon pyramidatus, without any reference to Rhind's 

 figure, and again as Unto pyramidatus. I am at present under the impres- 

 sion that Rhind's fig. b and Brown's pyramidatus are the same shell as the 

 present species, which I have ventured to describe under the name of 8. Salteri" 

 &c, &c. It is therefore apparent on that author's own showing that his specific 

 name cannot be retained, and I have therefore adopted Rhind's term Pentlandicus 

 as the specific name ; and indeed Mr. Etheridge goes on to say, " The posterior slope 

 of 8. Salteri is very frequently broken or crushed when the individuals bear a 

 close resemblance indeed to the above shells, in which there is no slope figured, 

 the posterior side consisting of a blunt acuminatum. If future investigation 

 should prove them to be identical, Capt. Brown's specific name Avill have to be 

 adopted." Apparently, therefore, Mr. Etheridge regarded Rhind's specific 

 name as a nomen nudum. 



I am inclined to believe that this species is of value as a zonal form, for it 

 seems to be confined to Calciferous Sandstone series, and never to be present in 

 the upper beds, which are characterised by the presence of Productus giijanteus. 



I have been fortunate enough to obtain very well-preserved examples of the 

 hinge of this species from Randerstone, Fife, and from Woodhall, near Edinburgh. 



The species is easily distinguished by its subquadrate posterior end and 

 moderate gibbosity from 8. axiniformis. It is relatively much more transverse 

 and more compressed than 8. carbonarius. 



Schizodus axiniformis, Phillips, sp., 1836. Plate XVI, figs. 10—15; Plate 



XVII, figs. 1—6. 



Isocaudia ? axiniformis, Phillips, 1836. Geol. Yorks., pt. 2, p. 209, pi. v, 



fig. 13. 

 Donax? sulcatus, Sowerby, 1840. Geol. Coalbrookilale, pi. xxxix, fig. 1 (explana- 

 tion of plates). 



