ANNULATA. 43 



"sombre shades " of the carboniferous forests were not"un- 

 cheered by the hum of insects ;" nor were the insects blind, 

 like those which now inhabit the vast caverns of Kentucky 

 and Carniola. The Articulata which come latest are the Cir- 

 ripedes, whose lowest family appears in the lias; while the 

 Balanidce are only found in the tertiaries. 



The number of fossil Articulata catalogued and described 

 forms but a very small proportion of those which have pro- 

 bably existed. Bronn enumerates 1551 fossil insects : 131 

 arachnids, 894 crustaceans, and 292 anellides. Darwin de- 

 scribes 69 fossil Cirripedes, 12 of which are living species. 



Class I.— ANNULATA. 



(Worms, Tube-Worms, Nereids.) 



Char. — Body soft, symmetrical, vermiform, annulated, with 

 suckers, or setae, or setigerous tube-feet ; blood of a red 

 colour in most. 



To certain small annelidoid burrows in the schistose rocks 

 of Bray Head, Wicklow, the name Histioderma has been 

 given ; but the peculiar markings on the surface of these and 

 other Cambrian rocks, e.g., of Arenicola didyma of the Long- 

 mynds, Shropshire, and ofScolithus linearis of the Welsh stiper- 

 stones and N. Amer. " Potsdam" sandstone, conjectured to afford 

 the earliest indications of the existence of marine worms, are 

 not without suspicion as to their origin. The so-called 

 "Nereites" bear considerable resemblance to other equally 

 ancient impressions which have been described as Zoophytes, 

 under the name of Protovirgularia (fig. 3, i). No such doubt 

 attaches to the worm-tracks which abound in the thin-bedded 

 sandy strata of the forest-marble ; and the " Cololites" of the 

 lithographic limestone are most probably the castings of worms. 

 Long calcareous tubes occur in the upper Silurian and carboni- 

 ferous strata, which have received the name of Serpiditcs ; but 



