424 



physiognomy, would, in the first instance, suggest. The form, 

 on the other hand, of the accessory oral organs, or maxillary 

 feet, which are here constructed so as to constitute organs of 

 attachment, as well as the singular development of the dorsal 

 arch of the posterior thoracic ring, and the connexion of the 

 feet of opposite sides, through the intervention of a large in- 

 tercoxal plate, — a striking feature in the greater number of the 

 suctorial Crustacea, but not found in the true entomostraca, — 

 unite with the semi-parasitical habits of Notodelphys in indi- 

 cating an affinity not to be mistaken with the true suctorial 

 tribes. 



Dr. Allman read another paper on a new Genus and Spe- 

 cies of Tracheary Arachnidans. 



In this paper the author described a Tracheary arachnidan 

 discovered by Dr. O'Brien Bellingham in the posterior nares 

 of a seal {Halichoerus gryphus). It turns out, on examination, 

 to be generally distinct from all the forms hitherto on record, 

 and Dr. Allman assigned to it the appellation of Halarachne 

 Halichceri, with the following generic characters : 



Halarachne,* Mihi. 



Gen. Cha.— Palps free, filiform; mandibles didactyle ; 

 sternal lip, bifid ; legs with the last joint terminated by two 

 hooks, and an intermediate three-lobed caruncle ; body entire, 

 elongated, sub-cylindrical, furnished anteriorly with a dorsal 

 plate; eyes, none. 



Species \xmca..—H. Halichceri. Hab.— Infesting the pos- 

 terior nares of Halichoerus gryphus, Irish coast. 



H. Halichceri possesses a very distinct tracheary system, 

 opening externally by means of two spiracles, which are placed 

 one at each side of the anterior extremity of the abdomen. 

 The alimentary canal, just before its termination at the pos- 



From aXg, mare, and apaxvr), (iranea. 



