1913. ] S. Kemp: Crustacea Stomatopoda of the Indo-Pacific Region. 19 
It will be noticed that the palp in this genus is either well formed and composed 
of three segments, or wholly absent ; no instances of a one or two-segmented palp 
have been observed. 
The inter-relationships of the Indo-pacific species cannot be traced with any great 
degree of satisfaction. S. vaphidea and S. annandalei, in the possession of large fixed 
spines on the penultimate segment of the raptorial claw, stand apart from all the rest, 
and the latter fall into two groups characterized by the structure of the fifth thoracic 
somite. The first of these groups contains the small-eyed species originally placed 
in. a separate genus, but linked to the more normal types by such forms as S. chlorida, 
S. fasciata, S. lata and S. gilesi. It also contains the highly-specialized deep-water 
section, comprising S. /eptosquilla and tenuispinis and a few isolated species, S. scorpio, 
S. armata and S. mantoidea. he second group, which in point of individual abund- 
ance greatly outweighs the first, contains a number of closely-allied species that fall 
into three sections, typified respectively by S. laevis, S. quinquedentata and S. nepa. 
In addition it includes four highly-specialized forms, S. investigatoris, S. costata, S. 
multicarinata and S. supplex. ‘The last is perhaps a remote connexion of S. laevis ; 
the other three appear to be early offshoots of the original nepa and quinquedentata 
stock ; but in each of them specialization has progressed on different lines. 
The species of Sguzl/a for the most part inhabit shallow water and seem to prefer 
sandy or muddy ground. ‘They construct burrows ; but as they frequently leave them 
in pursuit of prey, they are often taken in abundance in fishermen’s nets. Giesbrecht 
(1910) gives a valuable account of the bionomics of Squilla mantis in the Mediterranean. 
Brooks (1886, p. 168) states that ‘‘ Sguwill/a stridulates by rubbing the serrated 
spine of the swimmeret across the serrated ridge on the ventral surface of the telson. 
The noise which is thus made under water can be clearly heard above the surface.’’ 
This observation was made on Squilla empusa. Giesbrecht (1910, p. 201) found that 
Squilla mantis produced sound in a similar way, but only when it was grasped with a 
pair of forceps. From the structure and relative position of the parts the method of 
sound-production is not very clear ; but most Indo-pacific species possess a lateral 
carina on the under surface of the telson as in S. empusa and S. mantis, and it is prob- 
able, therefore, that stridulation is effected in the same way: my efforts to induce 
living Squilla to produce sound have, however, proved quite unsuccessful. Wood- 
Mason unfortunately gives no reason for his choice of stvidulans as a specific name and 
his specimens do not seem to possess any special structural distinctions which would 
furnish an explanation. 
KEY TO THE INDO-PACIFIC SPECIES OF Squilla. 
The following key to the Indo-pacific species of Squwilla is based on adult 
characters ; great caution should be used when employing it for specimens under 
40 mm. in length. 
I. Upper margin of propodus of raptorial claw with a series of fine and 
even pectinations in addition to a few movable spines at proximal end. 
