45 



CHAPTER III. 



MESOZOIC RADIATA*. 



Amorphozoa. 



Plocoscyphia laxa (M^Coy). 



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

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

 varying from half to 1 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 

 edges of the cups gives a superficial resemblance to some Lobo- 

 phyllm. 



Not uncommon in the greensand of Lyme Regis. 



{Col. University of Cambridge.) 



Jerea pastinaca (M'Coy) . 



Sp. Char. Very elongate- conic, subcylindrical, gradually tapering 

 towards the base (the extreme apex sometimes abruptly nar- 

 rowed), free end obtusely subtruncate with rounded margin, 

 but not contracted in diameter ; mouths of the vertical excre- 

 tory tubes rather less than a line in diameter, chiefly confined 

 to a circular area in the middle about half the diameter of the 

 individual, leaving an external margin about one-fourth the 

 diameter of a dense reticulated substance having a slightly 

 radiated structure in the cross section and destitute of the 

 large tubes. Average length 6 inches, diameter 2 inches, or 

 larger. 



This species resembles a carrot or parsnip in size and shape, 

 whence the specific name ; it is distinguished from the Siphonia 



* The new species in this chapter date from the ' Annals of Nat. Hist.' 

 for December 1848. 



