Oil Ancient Water-Jleas, ^c. 71 



up of a plexus of slender longitudinal unicellular filaments con- 

 stricted at intervals, and at the constrictions emitting a pair of 

 opposite decompound, dichotomous, corymboso-fastigiate liorizontal 

 ramelli, whose apices cohere and form a thin epidermal or peripheric 

 stratum of cells." It will be seen at once that this structure has no 

 resemblance whatever to anything existing in Prototaxites, even as 

 interpreted by Mr. C, and without taking into the account the fact 

 that Halimecla oijuniia is a small calcareous sea-weed, divided into 

 flat reniform articulations, to which this structure is obviously suited, 

 as it would be equally obviously unsuited to the requirements of a 

 thick cylindrical trunk, not coated with calcareous matter. 



In point of size, on the other hand, Mr. Carruthers adduces the 

 great Lessonia of the Antarctic seas, whose structure, however, is 

 not pretended to resemble that of Prototaxites except in the vague 

 statement of a pseudo-exogenous growth. Lessonia I have not ex- 

 amined, but the horny Laminarix of our North American seas 

 have no resemblance in structure to Prototaxites. 



Nothing further, I think, need be said in reply to Mr. Car- 

 ruthers' objections ; and Nematopht/cus may be allowed to take its 

 place along with a multitude of obsolete fucoids which strew the 

 path of palaeontology. As to Prototaxites, it is confessedly an 

 obscure and mysterious form, whose affinities are to be discussed 

 with caution, and with a due consideration of its venerable age and 

 state of preservation, and probably great divergence from any of our 

 modern plants ; and it is to be hoped that ere long other parts than 

 its trunk may be discovered to throw light on its nature. Until 

 that takes place, the above remarks will be sufficient to define my 

 position in regard to it ; and I shall dechne any further controversy 

 on the subject until the progress of discovery reveals the foliage or 

 the fruit of this ancient tree, belonging to a type which I beheve 

 passed away before even the Carboniferous flora came into existence. 



V. — On Ancient Water-fleas of the Ostracodous and Phyllopodoui 

 Tribes {Bivalved Entoniostraca). 



By Professor T. Kupert Jones, F.E.S., F.G.S. 



(^Continued from p. 193, vol. iv.) 



Pari 11. — Cypkidinad^. 



In the seas, chiefly of warm climates, numerous Ostracods are found 

 which possess a subglobular or subcylindrical bivalved carapace, 

 notched in its antero-ventral region, to allow of the play of the extruded 

 lower antennae, as locomotive organs, with a lateral movement. The 

 notch varies considerably in size and shape in difijerent genera. It 



