REPORT ON THE STOMATOPODA. H 



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 thetelson; 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 Lysiosquillw have, as a rule, the outer one of the two spines on the ventral prolongation 

 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 Coronida is shown, by the brackets, to share with Chloridella, 

 Coronis, and Protosquilla, its small eyes, uropods, and antennary scales; with Uiloridella, 

 Coronis, and Pseudosquilla the armed dactyle ; and with Protosquilla the small flat 

 carapace and acute rostral spine. 



