BRITISH SILURIAN BRACHIOPODA. 199 



specimens scarcely show any concentric wrinkles. Some Scottish specimens figured in 

 my ' Silurian Supplement ' show them very strongly marked. Besides the English and 

 Scotch localities already recorded, S. deltoidea has been collected by Mrs. R. Gray from 

 the Llandeilo at Craighead, Balcletchie, and Ardraillan Brae, in Ayrshire, as well as in 

 the Upper Caradoc at Drummuck, in the same county. 



ADDITIONAL NOTES WITH RESPECT TO RHYNCHONELLA. 



Since my descriptions of our Scottish Silurian species of Mhynclionella were put into 

 type, Mrs. R. Gray has kindly forwarded for my examination a number of specimens she 

 quite recently collected in Ayrshire, and this obliges me to refer once more to this very 

 difficult and complicated subject. 



In the Ayrshire Llandeilo both species and specimens of Bhyndionella are very 

 abundant, and this is the more remarkable as representatives of the genus are very rare 

 in the corresponding rock in other parts of Great Britain. Many more specimens of 

 some of the forms of the genus will, however, require to be collected and compared 

 before their characters can be fully determined, for they vary so much in shape and in the 

 number of their ribs that one is often very seriously at a loss to know where to draw the 

 line between two nearly allied so termed species. 



Thus, from the Llandeilo of Ayrshire I provisionally determine, describe, and 

 illustrate the following : 



\. Bhynchonella (JBmula,^dMQX. 2. MJi. Salteri ^J)si\. S. B/i. nasuta, M.' Coy. 4:. Bh. 

 Thomsoni, Dav. 5. Bh. PortlocJciana, Dav. 6. Bh. Lapioorthi, Dav. 7. Bh. sub- 

 dorealis, DsiV. 8. B/i. Peac/n,'Dav. 9. BL Weaveri F, Salter. 10. B/i. S/ialioc/densis, 

 Dav. 11. B/i. Scotica, Dav. 12. Bit. Girvaniensis, Dav. 13. Bh. BaldetcJdensis, 

 Dav. 14. Bh. cuneatella ; and one or two more forms approaching much in shape to 

 Bh. nucula are probably specifically distinct. This number is very large and still I have 

 not found it possible to reduce it with the material at my command, although two or 

 three of them are uncertain, and only provisionally named, for the sake of reference. 



37 



