44 Mr. J. W. Salter on the occurrence of a Fish 



inent of the rectum. Hepatic organ the same. Organs of ge- 

 neration double, occupying the middle part of the body; their 

 form undetermined. Ocelli at some distance from the head, of 

 the same colour as in U. infrequens. 



Size. l-7th of an inch long and l-600th of an inch broad. 



Male. The same as the female, but with a large, thick, curved 

 tail, obtuse at the extremity, tuberculated in its inner curvature, 

 and furnished on each side with a row of short seta? extending 

 from above the anus towards the tip ; also three or four setze on 

 the outer curvature. Testis and penis the same as in the fore- 

 going species ; form of the testis undetermined. 



Hah. Same. 



Loc. Island of Bombay. 



Urolabes parasitica, n. sp. 



Female. Linear, cylindrical, unstriated, gradually diminishing 

 towards the head, which is obtuse and without papillae, and also 

 towards the tail, which is long and conical. Mouth and anus 

 as in the foregoing species. Vulva a little in front of the middle 

 of the body. 



Alimentary canal and hepatic organ the same. (Esophagus 

 commencing in an expanded oral orifice, immediately becoming- 

 narrowed into a straight uniform tube ; naked at the commence- 

 ment, but soon surrounded by a sheath, which goes on increasing 

 in width to the point of union of the oesophagus and intestine, 

 after which it continues of uniform calibre to the termination 

 of the latter. Organs of generation double, occupying the 

 middle third of the body, their form undetermined ; filled with 

 ova diminishing in size with their distance from the vulva, and 

 all presenting the germinal vesicle. 



Size. 1 -43rd of an inch long. 



Male. Unseen. 



Hah. Peritoneal cavity of Nais albida, in more or less abun- 

 dance during the " rains," when this Nais makes its appearance 

 in the Gloeocapsa mentioned. 



Loc. Island of Bombay*. 



[To be continued.] 



IV. — On the occurrence of a Fish (Pteraspis) in the Lower Ludlow 

 Rock. By J. W. Salter, F.G.S. 



The discovery of a true Fish in beds of the Silurian system 



considerably older than the famous " bone-bed " of the Upper 



Ludlow rocks is a fact of much interest. It is desirable at once 



* For a small figure of this worm, see 'Annals,' series 3, vol. ii. pi. 4. fig. 50. 



