DAVIDSON — SCOTTISH CARBONIFEROUS BRACHIOPODA. 183 



pansions are wide, flattened, and clearly defined. The whole surface is covered 

 with numerous somewhat irregular transverse undulated wrinkles, while 

 numerous elongated pustules or tubercles are closely scattered over the entire 

 surface, and from which projected small adpressed tubular spines. The dorsal 

 valve is but slightly concave, with a small mesial elevation or fold ; it is like- 

 wise ornamented with numerous transverse wrinkles and elongated pits in lieu 

 of the tubercles observable in the opposite one. 



No Scottish interiors of this shell have been hitherto discovered ; but Eng- 

 lish specimens show that the muscular and other impressions did not differ 

 materially in detail from those of P. scabricuhcs and of others described in this 

 monograph. P. imstiilosus sometimes attained large proportions ; but the only 

 Scottish example I was able to examine did not exceed some eleven lines and 

 a-half in length by fourteen in width. 



In Haddingtonshire it is stated to occur at Cat Craig, near Dunbar ; and 

 another example, labelled from the north of Glasgow,* is preserved in the 

 Museum of Practical Geology. In Stirlingshire a specimen was found in shale, 

 under the Campsie main limestone by Mr. G. Somervile. 



The sixteen species of Productus described as having been found in Scotland 

 form part of Prof, de Koninck's following groups : — 



C Productus gifjanteus, Martin sp. 



Steiati ■< latissimus, J. Sowerby. 



(. cor a, d'Orbigny. 



Undati midatiis, Def ranee. 



semireticulatus, Martin sp. 

 Var. Martini, Sowerby. 

 costatus, J. Sowerby. 

 YoungiariMs, Davidson. 

 longispimis, J. Sowerby. 



Semiheticulati 



~ carbonarius, de Koninck, 

 spimdosm, Sowerby. 



Spinosi < scabriculus, Martin sp, 



Phillips. 



PiMBEiATi ( inmctatus, Martin sp. 



( jmwnatus, J . bowerby. 



Capeeati aculeatm, Martin sp. 



Mesolobi mesolobus, Phillips. 



It is probable that in time better and more abundant materials relative to 

 some few of the species will be discovered, and which will enable palaeon- 

 tologists to determine more exactly whether one or two of those above 

 enumerated might not be mere varieties of some already recorded species ; and 

 again whether we are justified or otherwise while considering P. Martini as a 

 simple variation in shape of P, semireticulatus. ^ Interiors of P. 



* The exact Scottish locality from whence this specimen, P. carbonarius, and Sp. pingtds 

 were obtained appears to be nnkno-wn. These specimens, which have all the appearance of 

 Scottish shells, are labelled "north of Glasgow" in the Museum of Practical Geology, but 

 were in all probabihty derived from some other portion of the country, for otherwise it would 

 be sti'ange that no examples of the two last have been met with by any of the collectors who 

 have explored with much care the numerous locahties to the north of Glasgow. 



t Mr. G. Tate, as well as some other palaeontologists, seem desirous of retaining P. semi- 

 reticulatus and P. Martini as separate species ; and Prof, de Koninck informs me that he now 

 feels uncertain whether the two should be considered as distinct. These shells have been 

 described separately in this monograph, && yar. semireticulatus and var. Martini ; and may 

 therefore be retained as specific denominations by those who might consider such a thing 

 desirable. 



