158 SILURIAN RADIATA. 



glass- like fibres exposed*. The analogy between those seems to 

 me very strong, and I know of nothing else in nature like the 

 fossil. I have named the genus from wvpiTTjf;, silex, and v^yita, 

 filum. Lest the specimen might be supposed to resemble a bun- 

 dle of certain Serpulcs, I may mention that the rods of silica are 

 not tubes, and have no walls. 



Strombodes Wenlockensis (M^Coy). 



Sp. Char. Corallum forming large irregular masses of polygonal 

 stems, the mouths of which vary usually from 8 to 10 lines in 

 diameter; boundary-walls strong, prominent, vertically sulcated 

 on the inside ; star depressed round the margin of the walls, 

 forming a large circular convexity nearer the centre, within 

 which is a concavity, from which rises the thick prominent 

 compound axis ; radiating lamellae twenty-four to twenty-nine, 

 strongest and most prominent on the circular convexity of the 

 star, where an equal number of small alternate ones disappear : 

 vertical section shows the thick central axis composed of irre- 

 gularly twisted plates, inner area a little narrower than the 

 outer area, from which it is separated by a solid vertical wall, 

 crossed by loose vesicular structure curving upwards and out- 

 wards, one or rarely two vesicular plates reaching across the 

 area on each side, vesicular plates of the outer area more curved, 

 slightly smaller, the rows inclining slightly upward and out- 

 ward, scarcely three cells in a row. A star 9 lines in diameter 

 has the prominent circular portion 7 lines in diameter, and the 

 prominent axis rather more than 1 line in diameter. 



To judge from the figure in the ' Silurian System,' that marked 

 t. 16. f. 8 « (not the 8 h), of Mr. Lonsdale's Acervularia Baltica 

 (Schw.), would seem to belong to this species, but according to 

 Phillips that has far more than thirty-six lamellse (Pal. Foss.) ; 

 the species represented by the latter figure has neither axis nor 

 divisional walls to the stars, and is certainly generically distinct 

 from Strombodes ; the true A. Baltica of Schweigger, according 

 to his reference to the ^ Amoenitates Academicse,' has no axis 

 and cannot belong to the present genus, of which this species is 

 the only one I am acquainted with in Silurian strata. The frac- 

 ture as usual passes through, and not between the columns, and 

 the buds are developed in the corners of the old stars. 



Not uncommon in the Wenlock limestone near Wenlock. 



{Col. University of Cambridge.) 



* I beheve M. Edwards considers this recent form to belong to the 

 Amorphozoa, and that the observed polypes were parasites. From the axis 

 of Antipathes beijig siliceous, I adopt for the present Mr, Gray's opinion. 



