BY JOHN MITCHELL. 551 



ciations. Other associates are some Spirifers, one of which has a strong re- 

 semblance to S. pittmani Dun, and with what appears to be a species of the genus 

 Seminula which would be an unexpected associate. 



Loc. and horizon. — Tydd's farm, Tulcumbali, Parish of Gunnenbene, County 

 Nandewar. If judged from the presence of Merista plebeia, the horizon would 

 certainly be declared Middle Devonian; but sliould the presence of Seminula 

 be proved, then the geological horizon of the rocks from which the fossils were 

 obtained will be a matter for reconsideration. 



ITXPLANATION OF PLATE XXXI. 



FigsA-S. ^Meris/a /i/efieia Sowerby. Ventral, brachial and profile views of mature speci- 

 mens. 

 Figs. 4-5. — Ret::ia salleri Davidson. Ventral aspect and weathered side of a specimen. 



In the latter six turns of a spiral are exposed. 

 Figs. 6-8 and H.-^Molongia elegans Mitchell. Dorsal, ventral, and profile views of three 



mature specimens (x 2); Fig. 12 has the dorsal valve removed to show the spires, 



enlarged. . 

 'F\<!,s.^-n.~Barrandel/a moloiigetiis Mitchell. Dorsal, ventral, and front views of three 



nearly mature specimens (x 2). 

 FiasA^-l^.—Sieberi'lla glabra Mitchell. Dorsal, ventral, and front views. Figs. 13 and 14 



are of adult specimens. Fig. 15 represents a shell of medium size. 

 Pigs. 16-20.— 6'/-///7.r (Sc/iizop/ioria) slrialiila Schloth. In figs. 16-19 the ventral, oblique, 



front and cardinal aspects are shown. Fig. 20 is the part of a cast to show the 



muscular scars of the pedicle valve, (x 3). 

 Figs. 21-22. —5/>w-;/fr boK'tiingensis Mitchell. Fig. 22 shows a specimen three-fourths 



grown (x i), and fig. 21 is part of a valve (x 3J to show the radial striae, etc. 



