70 DR. G. C. BOURNE ON THE RANINID^ : 
iintonnules and antennas are extraordinarily similar in Raninoides and 
Lyreidus (figs. 36-39) ; so also are details in the first and second and even in 
the third maxillipeds. In all these^things the relationship seems very close, 
but in other respects the two forms are divergent. In Lyreidus the eleventh 
sternum is large but narrowed between the arliculations of the first pereio- 
pods and pioduced backwards into two small pterygoid processes which 
form the sides of a hollow in which the last segment of the abdomen can be 
lodged, as described above. Owing to the presence of these pterygoid 
processes the twelfth sternum appears to be deeply fitted, but it is really 
short, narrow, and flat, in this differing much from Raninoides. The thirteenth 
sternum being also short the coxse of the first three pairs of pereiopods are 
close together, and in this respect Lyreidus resembles Notopus rather than 
Notopoides, Notosceles, or Raninoides. In the first and second pereiopods of 
Lyreidus the iscliiomerus is long, slender, and scantily fringed with hairs ; 
the carpus father short ; the propodus nearly twice as long as it is broad ; 
the dactylns elongate and almost styliform, with a strong external ridge. In 
the third pereiopods the propodus is about as broad as it is long and the 
dactylus cultriform. These are clearly digging and walking legs, and one 
may conclude that the descendants of a form in which reduction of the 
abdomen and last pair of legs led to the suppression of the posterior branchial 
orifices, diverged as they adopted a more exclusively swimming habit into 
Raninoides, as they became more exclusively burroweis into Lyreidus. 
Lyreidus must bury itself deeply, with the tip of its narrow elongated snout 
just breaking- the surface of the sand. Having no posterior branchial orifices 
it must be dependent on an inhalant current setting in somewhere in the 
region of the snout. One would expect some specialised inhalant apparatus, 
but there is very little evidence of such. Indeed, it is a singular thing that 
Ranina, Notopus, and Notosceles, all of which have well-developed posterior 
branchial orifices, have in addition much more specialised orbital and anten- 
nary arrangements for directing the flow of an incui'rent respiratory stream 
than have Raninoides and Ljyreidus, in which posterior respirator)' orifices are 
absent. In Notosceles the antennary structure is not very different from 
that oi Ranina. The flagellum is longer (figs. 41 & 41a), but the thick 
shortened segments of the peduncle, the.flabellate shape of the fourth joint 
with its fringe of plumose hairs, the greatly developed crest of the third 
joint also fringed with hairs, are very similar. So also is the flabellate shape 
of the basal joint of the antennules. Fig. 57 is a frontal view of the " face " 
of Notosceles shovving the antennae as nearly as I can draw them in their 
natural position. In the centre, below the rostrum, is the narrow exhalant 
passage bounded by the basal joints of the antennules. The orbits are closed 
below by the crests of third segments of the antennary peduncles, and the 
spaces below are filled in by the proximal segments of the antennae which in 
