COLURIDyE. 107 



This charming species, though in technical characters very similar to the preceding, 

 is yet readily distinguished when once it is known. It is very much rarer, averages nearly 

 twice its size, while its outline, in retraction, far more nearly approaches a circle. This, 

 with its crystalline brilliance, recalls the lovely Pterodince, of which it is no unworthy 

 rival ; and its resemblance to them is much augmented by a delicate line of corrugations, 

 which run round just within the margin, like the "milling" within a shilling. It 

 was this feature that suggested the specific name, and no allusion to the adjective solidus. 

 The arch of the lorica is much lower than in lepadella, especially towards the edge, 

 while down the middle there runs a very low, rounded ridge. The fore and hind exca- 

 vations are nearly as in lepadella. Besides the frontal hood, there is another clear disk 

 which appears to protect the rotating cilia, and a transparent bulb is placed on each side 

 of this, within each of which is seen a minute red eye, so that these organs are widely 

 separated. 



Some curious facts connected with digestion were illustrated by mixing a little car- 

 mine with the water. Particles were readily imbibed, and soon appeared as a red cloud 

 in the fore part of the stomach. Presently this pellet passed into the upbent viscus at 

 the bottom, which I supposed the intestine ; and a second pellet, swallowed at the same 

 instant, took the vacated place. After an hour, the whole alimentary canal had assumed 

 the appearance of fig. ll/, the supposed intestine being only a lobe or pocket of the 

 stomach. The pellet No. 1 now moved rapidly down to the cloacal extremity of the 

 twofold viscus, but, instead of being discharged, it swiftly passed up (as between the 

 dotted lines) to its first position at the base of the stomach ; then returned to the 

 cloacal end, and quickly again mounted ; repeating these movements several times, till 

 at length it coalesced with the second pellet. All the while the whole interiors of both 

 chambers were full of an incessant quivering from the action of epithelial cilia. From 

 all this, it really seems as if something analogous to rumination occurred in these minute 

 creatures. The gastric glands and the lateral canals are very abnormal ; and the con- 

 tractile vesicle is sometimes ample, sometimes totally wanting. P.H.G.] 



Length, T !- (7 inch. Habitat. Walthamstow ; Leamington ; Birmingham ; Woolston ; 

 Dundee (P.H.G.). 



M. ACUMINATA, EJirenberg. 



(PI. XXV. fig. 9.) 

 Mctopidla acuminata . . . Ehrenberg, Die In/us, p. 477, Taf. lix. fig. 11. 



[SP. CH. Lorica ovate, ending behind in an acute point ; occipitally deeply notched 

 between projecting spines ; the edges very thin. 



Besides the above peculiarities there is little to mark this obscure little species, which 

 yet is amply distinct. When seen sidewise it has much likeness to a Colurus, save that 

 its form is flatter ; and the decurved frontal hood is more conspicuous. It is an eager 

 and persevering feeder, raking with its hood-edge among the floccose, P.H.G.] 



Length. Of lorica, n i (T to ^j^ inch. Habitat. North London ; Leamington ; Sand- 

 hurst (P.H.G.) ; very scarce. 



M. OXYSTERNUM, Gosse. , 



(PI. XXV. fig. 8.) 

 Metopidia oxystcrnon . . . Gosse, Ann. Nat. Hist. 2 Ser. vol. viii. 1851, p. 201. 



[SP. CH. Lorica an ovate box of tesselated surface ; with a thin ridge running 

 down the dorsum ; venter with a similar medial ridge terminating abruptly in mid-length. 



This is a very curious form. It is a depressed rhomboid-oval, with a rather high and 

 thin arched ridge running down the back from the bottom of a deep frontal sinus. The 

 ventral surface is also ridged as far as the mid-length, where the ridge ends, like the 

 sternum of a bird. Then the surface is deeply excavated, and again projects, forming a 

 prominent sheath for the omission of the foot. The whole loiica is cut into facets, as 



