476 ON THE SPECIES UPOGEBIA STELLATA AND GEBIA DELTURA. 



tail differ also in some particulars, the exterior being rather broader 

 than it is long, and the middle one, or terminal segment, of the 

 abdomen nearly quadrate. In all other respects the two species very 

 greatly resemble each other." 



In a note Bell remarks : " The term ' deltoid ' appears to be very 

 much misplaced in describing this part." 



If Leach referred to the central lamella of the tail, the term is mis- 

 leading, as that plate is certainly subquadrate in form. But, as pointed 

 out by Stebbing {History of Cnidacca, p. 186), Leach was no doubt 

 referring to the minor branch of the Uropods, which may reasonably 

 be described as " deltoid." 



Bell further remarks : " I confess I am very douljtful if it will not 

 prove on further investigation that the two British forms, and perhaps 

 also G. littoralis of Eisso, constitute but one species. The form and 

 development of the abdomen, and the great development of the 

 abdominal false feet in G. dcltura, are certainly very much like 

 peculiarities belonging to the female sex, and calculated for the support 

 and protection of tlie ova." 



Norman appears to consider that there is only one species. In his 

 Crustacea of Devon and Cornvall, p. 12, he has : — 



" UpogeUa stcUata (Montagu) = Gdna dcUara (Leach)." 



At the Marine Biological Laboratory, I'lymouth, I have had the 

 opportunity of examining a good many specimens of both forms, both 

 alive and in spirit. The two forms are always found together at 

 Salcombe, and a day's hunting may produce a dozen specimens. Stellate 

 is rather more common than deltura. 



I have kept several of the stellata foyii in berry under circulation, 

 and the zoaeas have hatched out, and one specimen of the dcltura form, 

 in berry, which also hatched. In neither case, however, was I able 

 to rear the larVcT. There are thus males and females of both forms. 

 The genital opening of both forms is situated in the females on 

 the basipodite of -the 3rd thoracic appendage, and is covered by 

 a diaphragm. It is very easy to see. In the males, the opening is 

 on the basipodite of the 5th thoracic segment. Close to it, there 

 is a small tuft of setie. It is not so easy to distinguish as in the 

 female. 



The females of both forms possess modified copulatory appendages, 

 and may be recognised by them, as they are absent in the males. 



Among the Thalassinidte, Upogebia forms a rare exception to the 

 general rule on this point {vide Caiman, in Treatise of Zoolof/y, ed. by Bay 

 Lankester, part vii, p. 274). 



