REPORT ON THE STOMATOPODA. 
11 
and the presence of a median spine on the rostrum, while Protosquilla differs from all 
other Stomatopoda in the length of the acute median spine of its rostrum, and in the 
presence of acute long spines on its antero-lateral angles, and the union of the sixth 
abdominal somite with the telson ; and as it also exhibits, in its long rostrum, rudimentary 
uropods, and in the absence of a distinct sixth abdominal somite, a closer resemblance 
than any other adult to the Stomatopod larva, there can, I think, be no doubt that it is 
the most primitive genus in the order. 
I have attempted to give a graphic representation, in the following diagram, of the 
relationships between the genera of adult Stomatopoda, the heavy lines indicating their 
convergent relationship to each other and to Protosquilla. The characteristics which 
are joined by brackets to two or more genera are the features of resemblance between 
those genera, while those characteristics which are thus joined to only one genus are 
confined to this genus. 
The diagram is intended to express the relationship between the genera as established 
by the comparative study of all the species; and as it often happens that a feature which 
is highly characteristic of a genus as a whole may be absent or modified in a few 
exceptional species, the diagram cannot be used as a means of diagnosis. For example, 
the Lysiosquillas have, as a rule, the outer one of the two spines on the ventral j)rolongation 
from the posterior edge of the basal joint of the uropod longer than the inner, and I have 
therefore given this feature as characteristic of the genus ; for the study of the larvae shows 
that it is very significant, although it happens that there are one or two species in which 
the inner spine is the longest. 
While I trust that the diagram is quite intelligible, a word of explanation may be 
desirable ; thus, the genus Coronicla is shown, by the brackets, to share with Chloridella, 
Coronis, and Protosquilla, its small eyes, uropods, and antennary scales ; with C hloridella, 
Coronis, and Pseudosquilla the armed dactyle ; and with Protosquilla the small flat 
carapace and acute rostral spine. 
