432 MR,. P. H. GOSSE ON THE STRUCTURE, FUNCTIONS, AND HOMOLOGIES 
ing widely with IVot. aur'ita. The rami, when closed, assume a pyriform or lozenge- 
like outline, but are cleft to their base ; and as the unci are attached to the terminal 
half of their length, they open widely (fig. 24). 
57 . The whole manducatory apparatus in Anurcea acuminata bears a resemblance, 
singularly exact, to this of Not. clavulata, notwithstanding the external diversity of 
the two animals. The similarity extends even to the manner in which the unci, which 
are seven-fingered, are protruded into ihe, funnel, and fiercely snapped. 
58. Notommata 'petromyzon (Plate XVII. figs. 27 to 31) is remarkable for the ex- 
treme simplicity of the parts under review ; a circumstance which makes it peculiarly 
valuable as a study. It is one of those species in which the ciliated facial disk is very 
oblique, being nearly on the plane of the venter. Hence the buccal funnel is short at 
all times, and can be quite obliterated, the entrance of the mastax opening on the 
facial surface. This organ is a delicate sac with membranous walls, of obcordate 
form (fig. 31), deeply trilobate at the fundus. 
59. The fulcrum of the incus (fig. 31) is thin and blade-like ; straight, except that 
its free extremity is slightly incurved, very deep, and truncate at its articulate extre- 
mity. I’lie ra7ni (fig. 29), when united, form an isosceles triangle, cleft to the fulcrum 
and arching downwards. 
60. The mallei are equally simple. The manubrium (figs. 28, 31) is a slender rod, 
with a projecting process near its articulation. The uncus (fig. 28) consists of two 
fingers, membranous in texture, and at times evanescent, which work on the ramus 
near its extremity; and two muscular threads are seen connecting the former with 
the latter. 
61. Notwithstanding the simplicity of the organs in this instance, a comparison with 
Not. aurita will show that the structure is essentially the same in the two species. 
62. In Notommata lacinulata (figs. 32 to 34) the tnastax is very large, subtrihedral, 
with the orifice at the surface of the disk or protruding from it ; so that there is no 
buccal funnel. The incus, though somewhat simple, is very large; and the rami, 
when closed, form a hemispherical dome of thin texture; so as to resemble, when 
viewed obliquely from above (fig. 33), a globe of glass standing on a pedestal (the 
fulcrum). The similitude is enhanced by lines passing in different directions over 
the vault, like the astronomical circles. The mallei (fig. 34) are slender rods, hooked 
at the bottom; and soldered at the upper part across the dome, where they become 
very much attenuated, without any distinct division into manubrium and uncus. 
63. The rami of the mcus diVe divided to their base ; in use, they are protruded con- 
siderably, and are distinctly organs of prehension ; their edges being employed vigor- 
ously, in nibbling at the floccose matter that accumulates on aquatic plants, as the 
little animal crawls, by means of its two-toed foot, up and down the stalks. 
64. M. Dujardin has constituted a genus (Plagiognatha) for this species and Not. 
felis of Ehrenberg ; mainly, however, because they have “ machoires a branches 
parallHes tournees du meme cote, et recourb^es vers le bord cilie, avec une tige cen- 
