40 PAL2EONTOLOGY 



most probably the castings of worms. Long calcareous tubes 

 occur in the upper Silurian and carboniferous strata, which 

 have received the name of Serpulites. The Microconchus of 

 the carboniferous period is now regarded as an Anellide ; and 

 in all the later formations, tubicolar Anellides, especially of 

 the genera S&rpula, Sjnrorbis, and Vcrmilia abound. Some of 

 these, although attached and gregarious, are so regular in their 

 growth as to have been usually called Vcrmeti, but are now 

 placed in the genus Vcrmicularia. Spiroglyphus, and some 

 other shell-excavators, are indicated in the tertiaries. Amongst 

 the problematic fossils of the palaeozoic strata, two are supposed 

 to be anellidous, viz., the Tcntaculites (fig. 10, 7), which was 

 apparently free, and almost always regular in its growth, so 

 as more to resemble one of the gregarious Pteropods ; and the 

 Cornulite (fig. 10, s), which is attached when young, singly or 

 in groups, to Silurian shells and corals : the structure of its 

 shell is vesicular, and the cavity resembles a series of inverted 

 cones. The unattached and gregarious Ditrupa appears in 

 the upper chalk, and abounds in the London clay and crag. 



Class II. — CIRRIPEDIA. 



{Barnacles, Acorn- Shells.) 



Char. — Body chitinous or chitino-testaceous, subarticulated, 

 mostly symmetrical, with aborted antenna? and eyes ; 

 thorax attached to the sternal surface of the carapace, 

 with six pairs of multiarticulate, biramous, setigerous 

 limbs ; metamorphosis resulting in a permanent para- 

 sitic attachment of the fully-developed female to some 

 foreign body. 



The fossil Cirripedes belong chiefly to the sessile division, 

 and consist of the ordinary forms of the still-existing Bala n id Vr. 

 They are rare in the eocene tertiary, but more abundant after- 

 wards. The Balanus porcatus attains a great size in the shelly 



