DAVIDSON ON BRITISH CARBONIFEROUS BRACHIOPODA. 



55 



disposed to believe that Sowerby's figures of P. liemisplioericus, 

 belong to varieties of P. giganteus. This matter will be further 

 discussed in my monograph, for the limits prescribed to this commu- 

 nication will not permit of more lengthened explanations. P. 

 humerosus has been established on some singular internal casts; 

 the shell itself not having been hitherto discovered ; but I cannot 

 agree with those who would refer these casts to either P. giganteus 

 or P. semireticulatus. The prominences in the casts or deep conical 

 hollows (in the shell) for the accommodation of the oral arms indicate 

 that the ventral valve was enormously thickened. The position of the 

 adductor or occlusor muscle in the ventral valve is also slightly different 

 from that common to P. giganteus, and which would of itself, in this 

 instance, denote a specific difference. The material, however; is so 

 very imperfect and insufficient that very little can be said upon the 

 subject. P. proboscideus, and P. ermineus, P. arcuarius, are new 

 species to England, and a very interesting discovery entirely due to 

 the indefatigable exertions of my zealous and kind friend, Mr. 

 Barrow, who has in the most liberal and generous manner presented 

 me with his best, and by me figured specimens. The discovery of 

 P. proboscideus, (known in one Belgian locality only,) and of so 

 many other species at Settle, in Yorkshire, render that locality 

 especially interesting, as it exactly represents with us the equivalent 

 of the celebrated locality of Vise, in Belgium. 



P. sub-lcevis is also a new species to Britain ; but I am not yet 

 satisfied regarding the differences said to exist between it and P, 

 Christiani ; and should urge a search for more examples of both of 

 these large and almost smooth species of Productus. The first has 

 been obtained at Leek, in Staffordshire, as well as at Llangollen. 

 The second is stated by Prof, de Koninck to be from Wales, but of 

 which the locality is still unknown. 



P. Wriglitii is a small species with fringe, found by Mr. J. Wright, 

 at Midleton, near Cork, in Ireland, it differs from P. tessellatus in 

 several respects, and both appear good but rare British shells. 

 P. Youngianus has appeared to me new ; and in this opinion I am 

 supported by Prof, de Koninck, P. carbonarius (if a good species) is 

 decidedly very rare, for I have never seen more than two British 

 examples which would agree with Prof, de Koninck' s description and 

 illustrations of the species. The distinction between P. costatus 

 and P. muricatus are also difficult to determine, and I am now 

 disposed to believe that if the last is not a distinct species, it may 

 be a good variety of P. costatus. 



Productus sinuatus, under the designation ofLeptcena sinuata, appears 

 to have been noticed for the first time in England by Prof. M'Coy, 

 and. notwithstanding its well defined area, should be located under 

 Productus, of which it possesses all the characters, with the exception 

 of its well-defined ventral area, a character rare but not impossible 

 in the genus Productus ; and I am glad to find that Prof, de Koninck 

 entirely coincides with the opinions I have expressed upon the subject 

 relating to his remarkable species. P. sinuatus has also been recently 



