456 W. F. LANCHESTER. 



VII. Var. 'e.=festae. Nobili. 



Like var. oerstedii, but with spinules on the surface of the telson. West-American. 



Of these six (or seven ?) varieties, which I have grouped under heading three, the first 

 two, namely var. ananci/rus and var. acutirostris, differ so slightly in structure from G. chiragra 

 var. tumidus that it would be impossible to consider them as anything but varieties, and 

 as such they are estimated by Borradaile and de Man'. The other four present structural 

 differences of somewhat greater magnitude, and have been considered by their authors as 

 distinct species. I differ from these authors on the ground of later knowledge derived from 

 the study of the tumidus-glabrous transition-series, which shows (1) that the species as such 

 is highly variable and (2) that even structural differences as great as that between var. 

 tumidus and var. glabrous are connected by intermediates. In the case of var. spinosus and 

 var. espinosus we have no evidence of geographical isolation, the former being found both 

 at Mauritius and in the Maldives, the latter being founded on a single specimen only from 

 Rotuma; in the case of var. oerstedii and var. festae the evidence so far is in favour 'of 

 such isolation, and we may therefore conclude, for the present, that we are dealing in these 

 cases with distinct sub-species. 



KEY TO THE VARIETIES OF GONODACTYLUS CHIRAGRA. 

 Carinae sharp. 



3 carinae, well-defined. 



No definite spine on middle carina ; no anchor. 



Rostral angles blunt; carinae on submedian teeth not converging acutus 



Rostral angles sharp ; carinae on submedian teeth converging acutirostris 



A definite spine on middle carina; anchor present sniithii 



5 carinae, of which the submedian are more or less developed. 



Submedian carinae well-developed with spines glabrous (pars) 



Submedian carinae ill-developed, with or without spines segregatus 



Carinae blunt, swollen. 

 3 carinae. 



Telson spinous. 



An extra carina alongside carina on submedian teeth festae 



No extra carina spinosus 



Telson not spinous. 



Carinae very swollen, so as almost to touch each other espinosus 



Carinae not very swollen, with definite interspaces. 



An extra carina alongside carina on submedian teeth oerstedii 



No extra carina. 



6 marginal teeth, anchor present incipiens 



6 marginal teeth, anchor absent anancyrus 



4 marginal teeth, anchor absent tumidus 



5 carinae. 



Sutures on the terga of the abdominal segments graphurus 



Sutures absent; spines on the 3 middle carinae mutalus 



Sutures absent; no spines on the carinae glabrous (pars) 



1 Var. acutirostris, however, differs in a much greater a constant character ; a character which is so unusual in the 

 degree than does var. anancyrus if the convergence of the species that I have preferred to regard it as a possible 

 carinae on the submedian marginal teeth be taken as abnormality. 



