250 Messrs. Davidson & Morris on some species of Brachiopoda. 



Without the confirmation of stronger eyes and better knowledge 

 than I myself possess, I could not feel satisfied in recording any spe- 

 cies of Crustacea that can only be determined by microscopic power. 

 All those preceding the Entomostraca in arrangement came under 

 the notice of the former gentleman, and all of these (using the term 

 in its widest sense) under that of the latter. To both, my warmest 

 thanks are due, as they also are to John Edward Gray, Esq., for his 

 extreme kindness and liberality on this, as on all former occasions, 

 when I required to make use of the great national collection of zoo- 

 logy placed under his most zealous and effective superintendence. 



XXIII. — Descriptions of some species of Brachiopoda. By Mr. 

 T. Davidson, Mem. Geol. Soc. France, and Mr. J. Morris, 

 F.G.S. 



[With two Plates.] 



The following notice includes descriptions of a few new or little- 

 known Brachiopoda, some of which are interesting from their 

 localities and associations, more especially the Leptana, of which 

 three species have lately been found in the liassic group of En- 

 gland and one in that of France. For the description of the 

 French species we are indebted to M. Bouchard, whose collection 

 contains good specimens of this shell. 



Leptcena liasiana, Bouchard. PI. XVIII. fig. 2 a — d. 



Shell rounded, inequivalved, equilateral, smooth ; dorsal valve 

 gibbose posteriorly, becoming flatter anteriorly, with a slight 

 longitudinal groove ending in a notch on the front margin of the 

 shell. Beak small, slightly incurved, truncated at the apex by a 

 minute circular foramen, similar to that which occurs in many 

 other Leptance, for instance, L. alternata of Indiana, North 

 America ; this truncation may also be observed in some species 

 of Orthis from Russia. Area double, interrupted on the dorsal 

 valve by a large and slightly convex deltidium, which arises at 

 the apical opening and gradually enlarges towards the base, and 

 occupies one -third of the width of the area. The deltidium is 

 slightly notched, the notch being partly closed by the large me- 

 dian tooth of the ventral valve, the exterior face of which is 

 grooved by four furrows which afforded a passage for the mus- 

 cular fibres of attachment arranged in four bundles. The ventral 

 valve is deeply concave, following the contour of the dorsal valve, 

 so that little space remained between them for the body of the 

 animal. Cardinal margin about half the width of the shell. 

 Length 6, width 5 millimetres. 



Locality : the lias of Pic de Saint Loup, near Montpellier, 

 Herault. 



