1 68 DR. G. S. BRADY ON DIAPTOMUS SANCTI PATRICII 



An Amended Description of Diaptomus Sancti Patricii. 



By G. Stewardson Brady, M.D., LL.D., D.Sc, F.R.S. 



(Plate XL). 



In a recent volume of the " Proceedings of the Royal Irish 

 Academy,"* attention has been called to the imperfect 

 description of a fresh-water Entromostracan — Diaptomus 

 Sancti Patricii — published by me in the " Natural History 

 Transactions of Northumberland, Durham and Newcastle- 

 upon-Tyne," vol. xi., 1 89 1. This description was necessarily 

 imperfect owing to the scanty material then available, but 

 having recently (1909) re-discovered the species in Westmor- 

 land I propose now to describe it more fully. 



Mr. Scourfield's remarks are as follows — " Diaptomus 

 Sancti Patricii Brady. It is very unfortunate that this species 

 is not more certainly characterized, and that it should not 

 have been recognized since first taken by Brady in Connemara. 

 If it is really distinct from D. laciniatus it is one of the very 

 few species peculiar to the British Isles. If, on the other 

 hand, it is identical with that species, it is still one of the forms 

 linking the West of Ireland with Scotland and Scandinavia." 



Diaptomus Sancti Patricii G. S. Brady. Plate XI. 



Female. — Length 1*2 mm. Body slender; seen dorsally the 

 anterior portion (cephalothorax) about three times as long as 

 broad ; its anterior extremity obtusely rounded, posterior sub- 

 truncate, with acutely produced lateral angles, each ending in 

 a short spine. Genital segment of the abdomen about twice 

 as long as the combined length of the two following segments, 

 considerably dilated in front, and bearing a spine-like bristle 

 on each side ; caudal rami short, not much longer than broad. 

 Anterior antennae very slender, extending, when refiexed, 

 beyond the apices of the caudal setae. Basal joint of the last 



* Clare Island Survey, Part 46. Fresh-water Entomostraca by D. J. 

 Scourfield (Proceedings of the Royal Irish Academy, volume xxxi.). 



