CLAVELLATiE. 51 



Several examples of this species have been placed at my disposal from the Portland 

 strata of Wilts and Dorset, collected by the officers of the National Geological Survey, 

 and also by Mr. Cunnington ; neither of these, unfortunately, are altogether satisfactory. 

 The Survey specimens are deprived of their tests, as that of Plate IX, fig. 1 , which does not 

 exhibit the characters of the area. The specimens of Mr. Cunnington consist of portions 

 only with the test preserved ; fortunately the latter gentleman has also made a good 

 gutta-percha pressing, which exhibits the characters of the area as in the adjoining 

 woodcut ; together they afford sufficient materials to characterise the species. 



The present figure exhibits the entire area and escutcheon, together with the posteal 

 portions of the tuberculated costse. T. muricata has 

 a lengthened oblong figure, the length measuring 48 

 lines, the height 28 lines ; the anterior side is very 

 short ; the posterior side is much lengthened and atten- 

 uated ; the anterior and lower borders are curved ellip- 

 tically; the convexity of the valves is only inconsider- 

 able ; the umbones have but little elevation, but are distinctly recurved ; the area is large 

 and flattened, or is slightly convex posteally ; it has three tuberculated carinas, of which the 

 tubercles upon the marginal carina are regular, rounded, and rather distantly arranged ; the 

 transverse lineations upon the area are delicate and obscure, excepting the sub-umbonal 

 portion, where they become regular, ridge-like, and closely arranged, but are also small 

 and delicate ; the lateral costae have but little elevation ; they are very numerous (about 

 twenty-four), obliquely curved, and are nearly of equal size ; their anteal portions curve 

 nearly in the direction of the plications of growth, and become evanescent near to the 

 pallial border ; their tubercles are small, numerous, regular, and slightly compressed 

 laterally ; the larger tubercles occupy the middle and posteal portions of the rows ; they 

 are everywhere well separated. 



The more prominent features, as exemplified in the depressed, lengthened, oblong 

 figure, the very numerous rows of curved costse with their inconspicuous tubercles, 

 together with the delicate features of the area, separate it readily from other of the 

 British Clavellatce. In Portugal it also occurs in the Upper Jurassic Limestone at Torres 

 Vedras. 



