CRUSTACEA. 147 



thirds of each pleura is falciformly dilated into a thin, flat, 

 fin-like appendage, the anterior margin of which is very con- 

 vex, posterior margin slightly concave, extremity pointed ; py- 

 gidium small, the six marginal spines small, all extending to 

 about the same distance backwards, the anterior pairs there- 

 fore longest ; they are thick, triangular, and three or four times 

 wider than the others. Length of entire animal 1 inch 4 lines, 

 of glabella 5 lines, width about 9 lines. 



The disconnected, broadly falcate, paddle-shaped pleurae help 

 to distinguish this beautiful little species, which by its narrow 

 elongate form resembles a Remopleurides. One entire specimen 

 collected from the schists at Golen Goed, Myddfai, by Mr. Wil- 

 liams of Llandovery, and presented to Prof. Sedgwick by him. 

 {Col. University of Cambridge.) 



Ogygia radians (M^Coy), 

 Sp. Char. Py gidium nearly semicircular, slightly convex; axis 

 conical, undefined at the end, having three narrow segmental 

 furrows at the anterior end, lateral lobes with three broad ra- 

 diating ribs faintly divided at their axal ends by a small pleural 

 furrow ; margin tumid, entire. Length 4 lines, width 7 lines. 

 I provisionally give this name to a small pygidium not unlike 

 that of the Barrandia Cordai, but, from the duplicate lateral fur- 

 rows, belonging more probably to Ogygia] probably confirma- 

 tory of this view I observe in the 2nd Decade of the ' Geol. Surv/ 

 t. 7. f. 5. a small eight-jointed true Ogygia from Builth, having 

 the pygidium almost identical with the present species, if, as I 

 suspect, the duplicating furrows have been accidentally omitted 

 (the figure alluded to is given as the probable young of the 

 Ogygia dilatata (Phil.), a trilobite which has not been found at 

 Builth, but abounds in the schist at Waterford). 



Not uncommon in the black Wenlock shale of Pen Cerrig, 

 Builth. 



{Col. University of Cambridge.) 



Barrandia (M'Coy), n. g. 

 Gen. Char. Body ovate, depressed ; cephalic shield semicircular, 

 with the lateral angles produced backwards into 

 short spines; glabella widely clavate, the axal 

 furrow strong and nearly parallel at the base, 

 becoming obsolete towards the front ; eyes large, 

 narrow, reniform ; eye-line behind the eye cut- 

 ting the posterior margin about the middle, in 

 front of the eyes arching forwards, first out- 

 wards and then inwards ; thorax of seven seg- 

 ments ; axis convex, nearly as wide as the pleurjse, Barrandia. 



k2 



