RHYNCHONELLIDyE. 



157 



Position and Locality. P. glohosus is a rare fossil in either Upper or Lower 

 Llandovery beds. In the Lower Llandovery it is found at Pen-y-Craig, near Meifod, 

 North Wales, and Gorllwyn Fach, Llandovery. In the Upper Llandovery at Landeilo. 

 Messrs. PhilHps and Salter mention also localities in the Malvern district and the 

 Llandeilo district ; and Wooltack Bay, in Pembrokeshire. In addition to these, Prof. 

 M'Coy gives Beaver's Grove, Bettws-y-Coed, North Wales ; but Prof. M'Coy's fossil is 

 an Orthis, and from Caradoc rocks (J. W. S.). 



In Ireland, at Bally car, Co. Clare, and Kilbride (Mus. Geol. Survey, Ireland). 



Since the publication of my description of the genus Pentamerus, at p. 95 of the 

 " General Introduction," ' Monogr. Brit. Brachiop.,' vol. i, Mr. Billings has proposed to 

 detach from it certain species, such as Pentamerus liratus and P. lens, which he considers 

 to present differences of sufficient importance for the establishment of a separate genus 

 or sub-genus, for which he has proposed the designation Stricklandinia. The excellent 

 genus Pentamerus, which was established by J. Sowerby as far back as 1813, was typified 

 by the well-known P. Kniyhtii, characterised as " an equal-sided, inequivalved bivalve, 

 with one valve divided by a longitudinal internal septum into two parts, the other by two 

 septa into three parts or valves ; beaks incurved, imperforate." 



We will now reproduce Mr. Billings' description of his genus, as well as the reasons 

 why he considers it distinct from Pentamerus. 



Genus — Stricklandinia, Billinys. Stricklandia, ' Canadian Naturalist and Geologist,' 

 vol. iv, p. 132, April, 1859 ;^ altered to Stricklandinia, 'Can. Nat. Geol.,' vol. viii, 

 p. 370. 



" Gen. Char. Shell usually large, elongate-oval, transversely oval, or circular, some- 

 times compressed ; valves nearly equal ; a short mesial septum in the interior of the 

 ventral valve, supporting a small triangular chamber beneath the beak, as in Pentamerus ; 

 in the dorsal valve no longitudinal septa, spires, nor loop, yet observed ; the whole of the 

 internal solid organs (so far as is yet known) consisting of two very short or rudimentary 

 socket-plates, which support prolonged calcified processes for the support of the cirrated 

 arms. In all the species known the ventral valve has an area more or less developed. 

 The valves articulate by teeth and sockets. 



"This group of shells {Stricklandia), although closely related io Pentamerus, differs 

 from that genus in the following particulars : — 1st. In Pentamerus the form is globular, 



' Mr. Billings states, in the "Appendix" to vol. i of 'The Palaeozoic Fossils of Canada,' that, as the 

 generic name Stricklandia is preoccupied, he has changed it to Stricklandinia. He also informs me that 

 the only species of Rensselceria (Hall) claimed by him as a Stricklandinia is Vanuxem's Pentamerus 

 elongatus. 



