Mr. A. H. Hassall's Catalogue of Irish Zoophytes. .^Gl 



menibranaceous and cellular lungs ^vithout any gills for the 

 first class ; either gills in the early part of life, then cellular 

 lungs in their adult state, or gills or some branchial apparatus, 

 coexisting with cellular lungs through the whole of life, for 

 the second ; and gills only, without lungs, for the third class. 



Norton House, Stockton-on-Tees, April lOtli, 1811. 



[Note. — Mr. Owen nowhere assumes that the nose, as an absolute zoo- 

 logical character, is equal in importance to the lungs ; but believing, with 

 other Comparative Anatomists, that the air-bladder of the fish is essentially 

 a lung, and being able to trace its assumption of the true pulmonary st"uc- 

 ture within the undoubted limits of the class of Fishes, he is not disposed to 

 allow the respiratory organ to be so important, in relation to the classifica- 

 tion of the Lepidosiren, as the nasal organ, which manifests no essential al- 

 teration of structure in the class of Fishes ; but exhibits, throughout that 

 class, a marked distinction from the structure of the nose in Reptiles. Mr. 

 Owen's arguments for the essentially ichthyic character of the Lepidosiren 

 are based upon the cunmlative evidence of its dermal, dental, osseous, di- 

 gestive, sensitive and generative systems, rather than on any single and ar- 

 bitrarily chosen character. — See his 'ConcludingObservations,' Linn. Trans,, 

 vol. xviii. p. 350 ; also the Proceedings of the Microscopical Society at p. 211 

 of our present volume, containing Mr. Owen's examination of the structure 

 of the teeth, which he finds to be altogether such as is peculiar to Fish. 

 The new naming of the genus we cannot approve. — Ed.] 



XXXIX. —Supplement to a Catalogue of Ii'ish Zoophytes. By 

 Arthur Hill Hassall, Esq. Read before the Natui'al 

 History Society of Dublin, November 6th, 1840. 



[Concluded from p. 287.] 



Valkeria tmhricata. " Cells in dense clusters, irregularly scattered 

 on the polypidom," cylindrical. Plate VIII. fig. 2. 



I have added to the usual definition of this species the word cy- 

 lindrical, as the form of the cells is the most important practical 

 point of distinction between it and the preceding species. Valkeria 

 imbricata, in the first stage of its formation, consists of a single layer 

 of cells spread over the surface to which it is attached (usually 

 Fucus vesiculosus), and not rising from it in the form of an inde- 

 pendent polypidom. In this stage of its gro\Ai;li it constitutes the 

 Boiverbankia densa cf Dr. P'arre. This fact I have ascertained from 

 a comparison of Dr. Farre's figure and description of that species 

 with it, and its concurrence with these is so close as not to admit of 

 a doubt upon the subject. Bowerbankia densa is, therefore, not a 

 distinct species, but merely a condition of the well-known one, Val- 

 keria imbricata. Although the examination of numerous specimens 

 of V. imbricata which I have made has resulted in the eradication 

 of B. densa as a distinct species, I yet must not omit to notice the 

 admirable memoir published in the ' Philosophical Transactions,' 

 ujjon this and an allied species by Dr. Farre, the gentleman by 

 whom Bowerbankia densa was first described and figured as a di- 



