AFFINITIES OF THE GENUS SIPHONIA. 795 



this is succeeded by a true S. pyriformis, but with faintly longitu- 

 dinally wrinkled sides ; then follows P. biloba (S. costata), which 

 shows the incipient lobation of the preceding in a more advanced 

 stage ; from being irregular and vague, it has become definite, and 

 exhibits two regular longitudinal ribs. The lobation thus commenced 

 is continued by specimens with from three to six or even seven 

 lobes : so great, indeed, is the tendency of this form to lobation, 

 that in P. triloba the three principal folds are in one specimen sub- 

 divided into secondary ones by a depression running longitudinally 

 down each ; and in a variety of P. seccloba the six chief ribs are 

 also separated into secondary ones, but in this case by transverse 

 instead of longitudinal constrictions. So easy do the transitions 

 between the varieties in this series appear to be, as to leave great 

 doubt in one's mind as to the specific distinction between the 

 extreme forms of S. pyriformis and S. costata. 



1832. Passy. ' Description geologique du departement de la Seine- 

 Infe'rieure, p. 339, pi. xvi. fig. 9. 



In this work we merely find a notice of the occurrence of a form 

 which the author calls Clwanitcs pyriformis, a variety of G. Koaigii. 

 It is from the Upper Chalk in the department of the Eure, and 

 appears from the figure to be a small form of C. Kbnigii. 



1830-37. Fischer-dc-Waldheim. ' Oryctographie du Gouv. de Mos- 

 cou,' pp. 178, 179, tab. xlviii. figs. 3 and 4. 



The genus Siplionia is here included with the Polypiers, and Gold- 

 fuss's definition is repeated. A new form is figured and described 

 as S. radiata, a variety of S. pyriformis, from Bouchevoe, ten 



rsts from Moscow, in Upper Chalk. 



1831. Blainville. ' Manuel d'Actinologie,' p. 536, pi. 95. fig. 1. 



Blainville defines the genus according to Goldfuss, and enume- 

 rates as its species S. pyriformis, excavata, praimorsa, pistillum, 

 inerassata, and cervicornis. A recent sponge from the Mediterranean, 

 exhibiting a certain superficial resemblance to Siplionia, is referred 

 by Blainville to this genus, and not only so, but constituted its 

 type, under the name of Siplionia typum, Do Blainv., pi. 95. fig. 1, 

 Mers de Sicile. 



Now, in the first place, this S. typum appears to me to be iden- 

 tical with the Alcyonium ficus, Linn., described by Count Marsilli, 

 and considered by Scheuchzer and Parkinson to be the living repre- 

 sentative of SipJionia, for which reason they referred Siplionia to 

 Alcyonia. Thus this particular species (S. typum*) has considerable 

 interest for us, especially as it was adopted so recently as 1867 by 

 the late Dr. Gray, who introduced it into his proposed arrangement 

 of the sponges as a member of the Keratacea (Proc. Zool. Soc. 

 1867, p. 509). The fossil Siplionia, however, is, as we shall show, 

 a Lithistid sponge ; and it would certainly be curious if a recent 



