A STUDY IN CARCINOLOGY. 71 
i-beir tnni are overlapped by the broad anterior margins of tbe meri of the 
third maxillipeds. The left antenna is closed nearly as far as it will go 
against the aritennule, and this is the more normal position : that of the right 
side (the spectator's left) has been pulled outwards to show the passage 
between the third and fourth joints of the antennary peduncle and the basal 
joint of the antennules. Through this passage water can pass from the 
orbits to the itihalant chamber covered in below by the meri of the third 
maxillipods. The arrangements are very much the same as in Raniiia though 
somewhat less highly specialised. In Raninoides (figs. 36 & 37) and Li/reidus 
(figs. 38 & 39) the basal joints of both antennules and antennae are longer 
and more slender, and to that extent more primitive than in Notosceles and 
Ran'ma. In the antennules the admediau surfaces of the basal joints of the 
antennules are expanded and somewhat concave, so that when opposed they 
form a conduit for the exhalant current. The third segment of the anten- 
nary peduncle is long ; a good deal longer in Lyreidus than in Raninoides. 
The crest is prominent but narrow, and extends nearly as far forward as the 
end of I he fourth segment. The proportions differ slightly in the two species, 
but the general character is the same. The nature and distribution of the. 
hairy fringes are clearl}' shown in the drawings. The relative positions of 
the antennules and antenuse are shown in fig. 58 for Raninoides : they are 
hardly different in Lyreidus. It will be observed that the "spout" of the 
antennary sternum is produced to open well forward between the basal joints 
of the antennules : it hardly extends as far forward in Lyreidus. In both 
genera, but to a greater extent in Lyreidus than in Raninoides, the third 
peduncular segment of the antenna is overlapped by the tip of the elongated 
merus of the third maxillipeds, and the portion not overlapped is covered by 
a tuft of long hairs projecting forwai'd from the tip of the merus. The inner 
faces of the tliird peduncular segments of the antennpe and their crests are so 
shaped that when bent inwards they fit very exactly to the outer surfaces of 
the basal joints of the antennules, and when in this position completely bar 
the passage of water from the orbits to the inhalant chamber above the third 
maxillipeds. But when the antennae diverge slightly outwards a clear 
pas>age is left between the antennules and the antennfe, and the intrusion of 
sand is guarded against by the overlapping bristles of both. Through this 
passage, I think, the inhalant current must pass when the scaphognathite is 
working normally, and through it the excurrent stream must flow when the 
action of the scaphognathite is reversed. But the subject is very obscure, 
and I am by no means content with this explanation. I gi've it for what it is 
worth in the hope that some favourably placed naturalist may read it, find 
fault with it, and straightway proceed to make observations and experiments 
on the living animals. The results cannot fail to be of interest. I feel 
certain only of this, that there is an inhalant current between the third and 
