Plumularia. Z. HYDHOIDA. 145 



I have a specimen of PI. cristata gathered in Cork Bay, and present- 

 ed to me by J. V. Thompson, Esq., which is nearly 3 inches in height, 

 spreading laterally, the rachis divided in a regular dichotoraous man- 

 ner, and rough or muricated on one side, wherever it is naked of 

 pinnae. The vesicles have from 7 to 9 crested ribs with a spinous 

 dorsal keel. The roughness of the I'achis is produced by the remains 

 of the deciduous pinnae. I give a figure of this specimen, (Plate XX. 

 Fig. ],) as an additional proof that little reliance can be placed on ex- 

 ternal habit as a character in determining the species of this order. 



3. P. PENNATULA, plumous, the pimia opposite ; cells in a 

 close roio, cup -like icith an unequally crenated margin, support- 

 ed on the under side hy a lengthened incurved spinous process. 

 Montagu. 



Plate XVIII. Fig. 1, 2. 



Sertularia perinatula, Ellis and Suland. Zooph. 56, tab. 7, fig- 1, 2- Bosc, 



Vers, iii. 114. Fleming m Edin. Phil. Journ. ii. 83 Aglaophenia 



pennatula, Lamour. Cor. Flex. 168. CoraU. 74 Plumiilaria penna. 



tula, Lam. Anini. s. Vert ii. 128. 2de edit. ii. 165. Flem. Brit. 



Anim. 546 La P. pennatule, Blainv. Actinolog. 478. 



Hub. Coast of Devonshire, rare, Mr Montagu. 

 " This coralline is as remarkable for the elegance of its form, as its 

 likeness to the feather of a pen." Specimens from the seas of tropi- 

 cal climates are from 5 to 6 inches high, but my British specimen, 

 which I owe to the liberality of J. E. Gray, Esq., is scarcely one inch 

 and a half. The polypidom rises from implexed tubular fibres : the 

 lower portion of the cylindrical jointed rachis is naked, the upper 

 pennate and gracefully proportioned. The cells are small with a 

 waved margin and a little spine on each side, and they are seated in 

 the axil of a long tubular incurved process which rises much above 

 them. Lamouroux has conjectured that the PI. pennatula of Flem- 

 ing is only a repetition of PI. myriophyllum ; and Milne-Edwards 

 refers it to PI. cristata. I cannot see the slightest foundation for 

 these suspicions. 



4. P. FINN at a, stem plmnous, the pinnce alternate ; cells ra- 

 ther distant, one on each internode, campanulate, leaning, the 

 mouth entire ; vesicles ohpyriform, strongly toothed above. Dil- 



lenius.* 



Plate XVII. Fig. 4, 5. 



* Born in 1687 at Darmstadt in Germany ; came to England in 1721 ; and died 

 at O.xford in 1747. He was the first Professor of Botany there, and has not been 

 equalled in celebrity by any successor. It is unnecessary to give particulars of 



K 



