KEMP—PELAGIC CRUSTACEA DECAPODA 65 
Oct. 16, 1905. 4 miles N.W. of Desroches Atoll. Il. 750 to 0 fms.; two young, 
22 and 36 mm. 
Acanthephyra purpurea has not hitherto been recorded from the Indian Ocean. 
Judging from the fact that no specimens have been obtained by the “Investigator,” it 
seems probable that it does not occur in the more northerly portions of this region, but is 
replaced in the Arabian Sea, the Bay of Bengal and the Andaman Sea by its near ally, 
A. sanguinea. From this species, as Alcock has pointed out, it is readily distinguished 
by the presence of a prominent branchiostegal spine which is buttressed by a short 
carina. ‘ 
Little indication of the great variation which is known to exist in the species is 
shown in the six adult examples contained in the collection. The rostrum is in all cases 
longer than the carapace and its dorsal and ventral teeth are well spaced; the telson 
extends noticeably beyond the uropods and bears from four to five dorso-lateral spinules. 
In these features the specimens closely resemble the type (from the Atlantic) figured by 
A. Milne Edwards, and differ from the form found most commonly, though not invariably, 
in the N.E. Atlantic. Coutiére (Joc. cit., p. 18) recognises the form with numerous 
spinules on the telson under the name, var. multispina, but considering the enormous 
range of variation which is known I am not of the opinion that such details merit 
recognition in the nomenclature. 
The specimens in the collection exhibit the following rostral armature : 
BEEGG4 B18 
The eyes are in most cases damaged. In examples in which they exist the cornea 
is of a dark reddish brown and is not jet-black as in all other examples that I have 
examined. Differences in eye-colour seem to afford useful taxonomic indications; in the 
present case the colour may have been altered by prolonged immersion in formalin, though 
such treatment does not appear to have had this effect in Notostomus and Sergestes. 
Notostomus, A. Milne Edwards. 
In determining the solitary example of this genus contained in Mr Gardiner’s collection 
I have had occasion to consider the known species as far as it is possible to do so from the 
published descriptions, and, with a view to affording some slight assistance to those who 
may subsequently be working at the genus, I have appended a partial synopsis of the 
twelve that have been described. 
The knowledge acquired within recent years of the considerable post-larval changes 
that occur in an allied genus leads one to suppose that, with the acquisition of more 
abundant material, the present taxonomy of Notostomus must be subjected to revision. 
In species of Acanthephyra there is often a great range of variation in regard to the 
length of the rostrum and the dorsal armature of the abdominal somites, and, in the case 
of the former character, it has been shown that this variation is largely correlated with 
growth. In very young post-larval examples of Acanthephyra purpurea the rostrum is 
short ; at a later stage, before the fully adult phase is attained, it has a comparatively 
great length, whereas in the adult it again becomes relatively short, but not so short as 
SECOND SERIES—ZOOLOGY, VOL. XVI. 9 
