Mr. F. M'Coy on some new Mesozoic Radiata. 397 



be taken for the Amphipeplea involuta of Thompson ; but it may 

 be distinguished from that shell by its being stronger and more 

 ventricose, and especially by its having the whorls placed more 

 to one side, giving it somewhat the form of a Nerita. When full- 

 grown it is more than three times the size of A. involuta. 



It differs from all the varieties of Limncea peregra in having the 

 spire involuted and placed rather more obliquely, in the more 

 gibbous and ampuUaceous form of the shell, and in being more 

 regularly striated. The animal, too, is much darker, and not so 

 distinctly marbled on the cloak. 



A shell found by Capt. Brown in Loch Leven, and described 

 and figured in his ' Illustrations of Recent British Conchology ' 

 under the name of Amphipeplea lacustris, appears to resemble 

 this species in form, but it is stated to have the spire with two 

 small volutions, the superior one blunt at the apex, from which 

 we must conclude that the spire is exserted : the shell is also 

 stated to be ^ extremely thin, pellucid and shining ;^ — characters 

 which agree much better with Amphipeplea glutinosa than with 

 our shell. The Gnlnaria lacustris of Leach, to which Capt. Brown 

 refers his species, is quite distinct from the one now described. 



Mr. Burnett first detected this new Limnaa in the stomachs 

 of trout caught in Loch Skene, and on a second visit to that wild 

 locality, so tempting to the angler, he succeeded in obtaining 

 many fine living examples, for the larger portion of which I am 

 indebted to his liberality. Some of the older individuals are a 

 good deal eroded and perforated, showing that they have other 

 enemies besides the trout. 



XLII. — On some new Mesozoic Radiata. By Frederick M'Coy, 

 M.G.S. &N.H.S.D. &c. 



Amorphozoa. 



Plocoscyphia laxa (M^Coy). 



8p. Char. Hemispherical masses about 2 or 3 inches in diameter, 

 formed of short, wide, irregularly contorted and lobed cups, 

 varying from half to I inch in diameter, the walls about 2 lines 

 thick, of a rather coarse irregular spongy texture. 



On comparison with the figure of Goldfuss, and with authentic 

 specimens from the Essen chalk of his Achilleum morchella, which 

 now forms the type of the genus Plocoscyphia of Reuss, I find 

 the present species distinguished by its much larger, more deeply 

 and widely separated cups, their much thicker walls, and very 

 much more open lacunose structure. The contortion of the 



