NOTOMMATAD^E. 23 



N. PILARIUS, Gosse, sp. nov. 



(PI. XVII. fig. 5.) 

 Notommata tripus . . . . Ley dig, Ueb. d. Bau d. Raderth. p. 37. Taf. iii. fig. 28. 



[SP. CH. Body (viewed dorsally) rhomboidal in outline, sub-truncate at both ends ; 

 head broad, with great globose auricles ; brain pointed, filled to a greater or less extent 

 with opaque matter ; tail and toes as in N. tripus. 



This little creature has much likeness to the preceding, from which, however, it 

 sufficiently differs in the trapeziform outline, tapering from the middle to the foot ; in 

 the size and form of the auricles, which are very large, hyaline, and round, more than 

 a semi-globe being exposed ; in the conspicuous eye ; in the singular overarching of. the 

 edges of the dorsal region, like the carapace of an Oniscus. Mr. Perty mentions this 

 peculiarity in his N. onisciformis ; yet a glance at his figure proves that the two species 

 are not identical. The singular effect produced when the little creature suddenly pushes 

 out, and as suddenly withdraws, its frontal balls of glass, reminded me of the ancient 

 pilarii, or jugglers with balls, and suggested a specific name. 



The great transverse diameter of the body is remarkable. The rhomboidal outline 

 has much of the appearance of a lorica ; for it is constant, and the viscera within take 

 the form of great sacculate lobes, varying, and more or less receding, from this outline. 

 The brain is a large, perfectly defined opaque mass stretching almost wholly across the 

 head. 1 There seems to be a very minute crimson eye-speck in the centre of the front, 

 discernible with difficulty. The contractile vesicle is very large ; its period of discharge 

 was just two minutes. The globular auricles are exserted only at uncertain intervals, 

 as when the animal wishes to swim swiftly. We may watch one by the hour, creeping 

 up and down the stems, nibbling ever as it goes, or even now and then slowly gliding 

 through the clear water ; yet not once see the crystal balls thrust out by the little 

 juggler. Yet is he unmistakable, in whatever condition, when once familiarly known ; 

 and a very pretty, attractive little fellow he is. 



I first became cognizant of it in February 1855, when examining a tangle of conferva 

 and Nitella in one of my window-reservoirs at Torquay. But I have since met with it 

 on many occasions and in many waters. It is moderately lively, actively grubbing 

 about the vegetation and sediment, now and then swimming across the open spaces, 

 generally with little speed or energy, till the great glassy globes are set to work. The 

 interior structure calls for no special notice. P.H.G.] 



Length, ^^ inch; breadth, ^^ inch. Habitat. Woolston Pond : common (P.H.G.). 



N. FOKCIPATA, Ehrenberg. 

 (PI. XVIII. fig. 1.) 



Notommata forcipata . . . Ehrenberg, Die In/us. 1838, p. 428, Taf. li. fig. 5. 



[SP. CH. Form lengthened, saccate, large in front, tapering to a small foot, and 

 very minute furcate toes; occipital end of brain semi-opaque, a small inverted pyramid ; 

 eye a broad transverse lens. 



This is an active, graceful, attractive animal, somewhat sack- or purse-like, slender 

 behind, but enlarged towards the head, which is in constant contraction. The front is 

 obtuse in the dorsal and lateral aspects; the face is slightly prone. Behind a large 

 mastax of normal jaws, very protrusile, an ample brain descends into the occiput, 

 whose pyramidal tip, for a small space, is occupied by a well-defined granulation of clear 

 brown tissue, not white by reflected light, and so not cretaceous ; on the frontal end of 

 which is seated a broad, somewhat square eye of pigment darkly red. Two small ciliate 



1 From this transverse development of the opaque chalk-masses, I infer that Dr. Leydig's tripus is 

 this species. 



