336 MB. E. S. COBBOLD ON THE [vol. lxxvi, 



Provisional diagnosis. — General outline either transverse or 

 elongate oval. Ventral valve convex, with apex recurved over 

 or beyond the posterior margin ; anterior slope convex, with gently- 

 lessening curvature, lateral slopes rather natter ; lateral angles 

 rounded ; posterior slope continuous with the lateral, without any 

 defined false area; pedicle-opening indicated by an arching upwards 

 of the posterior margin ; shell-substance corneous or calcareo- 

 corneous, consisting of three principal layers, of which the exterior 

 is marked by numerous concentric impressed striae with flat bands 

 between them, the intermediate layer is marked by impressed lines 

 radiating from the apex, and, towards the margins, by impressions 

 of the concentric bands of the exterior, wdiile the innermost layer 

 is smooth so far as known. 



Dorsal valve, not known with certainty. 



Type species — Walcottina lap worth i, sp. nov. 



Horizon — Lower Cambrian of the Comley district, Shropshire. 



Walcottina lapworthi, sp. nov. (PL XXI, figs. 23«-23c, 

 24a-24'&, &25.) 



Cobbold, 1916. Rep. Brit. Assoc. 1915 (Manchester), p. 118, ' brachiopod allied 

 to both Miekwitzia and JLutorgina .' 



Type-specimens [King la & 1&] in the Geological Survey col- 

 lection. 



Diagnosis. — Ventral valve: outline transversely oval, lateral 

 angles rounded, posterior margin nearly straight and transverse to 

 the axial line for about three-fifths of the width ; convexity well 

 marked ; apex somewhat recurved and extending well behind the 

 posterior margin ; anterior slope of fairly even curvature, though a 

 little flatter towards the front margin ; lateral slopes tending to 

 flatness towards the lateral angles ; false area and pseudodeltidium 

 not developed ; shell-substance corneous, composed of tw T o principal 

 layers of moderate thickness, and an inner one which appeal's to be 

 very thin ; exterior marked by concentric, impressed lines, spaced 

 fairly regularly at 7 or 8 to the millimetre, the interspaces being 

 of the nature of flat bands, stages of growth indicated by an occa- 

 sional strengthening of the concentric lines ; interior layer of shell 

 marked by many gentle corrugations radiately arranged, and dying 

 away towards the half-length of the shell ; third and innermost 

 layer smooth, so far as seen. 



A comparison between the external view (fig. 23) and that of 

 the interior layer (fig. 24) shows that the outer layer of shell was 

 thickened round the base of the apical portion, so that the apex in 

 the latter figure is more acuminate than it is in the former. 



Dorsal valve, not known. 



The type-specimens were collected by Mr. W. Wickham King, 

 and presented bv him to the collection which was being made in 

 1892 by Mr. J. Rhodes. 



The species is dedicated to Prof. C. Lap worth, who suggested a 

 reference to Miekwitzia in the field at the time when the specimens 

 were found. 



