90 Transactions of the nZll^'%Tl'^1o' 



In Pierogorgia setosa, for instance, we for tlie first time meet 

 ■with an arcuate form bearing tuberculas only on the inner surface 

 of the arc (Plate XLIL, Fig. 22). These viewed in profile bear a 

 grotesque resemblance to a canoe fully manned, and for which 

 reason I shall hereafter distinguish this form of spicula by the 

 appellation of the scaphoid type.* Mixed with these, in P. setosa, 

 is the Leptogorgian type before referred to. Pt. pinnata also 

 possesses the two forms which obtain in the last-named species. 

 P. suherosa and hetuUna possess, in addition to the Leptogorgian 

 type, spicula of a somewhat ovate form (Plate XLII., Fig. 20); and 

 with the latter are also included an approach to the Juncella 

 and spiked dumb-bell type.f The spicula of P. iKtecliizans and 

 laxa also follow the Leptogorgian type, but are rather irregular. 



Xiphigorgia. — Polypary having the sclerobasic axis bordered 

 on each side by a lateral expansion of the coenenchyma ; the cahces 

 disposed in vertical rows on the edges of these laminae. 



The Leptogorgian type of spicula, with minor modifications, 

 is predominant in both species of this genus ; X anceps possessing 

 in addition an approach to the scaphoid type. 



Rhipidigorgia. — The branches of the polypary in this genus 

 are not only disposed on the same plane, but the ramuscules 

 coalesce at every point of contact, so as to constitute a more or less 

 perfect network. This form of polypary has won for them the 

 popular appellation of " Sea-Fans." 



Milne Edwards refers to this genus all the Gorgonacese ex- 

 hibiting a tendency to become reticulate ; but as such an arrange- 

 ment necessarily binds together a series of species presenting the 

 most marked differences in the structure and arrangement of their 

 calices, in the contour of their respective spicula, and, in all pro- 

 bability, in that of the polyp-animals themselves, the genus, as 

 at present constituted, cannot take rank as a natural one. 



The following are the principal modifications in form of the 

 spicula of the species I have so far examined : — 



1. Bhijndigorgia jlahellum and occatona agree in possessing 

 the Leptogorgian and scaphoid type combined. 



2. a. reticidum, crihruni, arenata, verriculata, and stenohracMs 

 abound in the Leptogoigian type alone. 



3. B. lacuens, plagalis, and umhracidum differ in possessing 

 the form peculiar to Juncella. 



4. B. strida and coarctata vary again in the possession of an 

 arcuate in conjunction with a laminato-proliferous type, referred 

 to when describing Echinogorgia, and in which genus they were 

 then included. 



* Kolliker ilistinguishes tliis as the " cramp-iron " form " kluMmer," but tlie 

 simile sceins scarcely dciinitive. 



•j- SubbcquL'ut examination baa led me to refer this species to Juncella. 



