CRUSTACEA. 



143 



a vegetable nature, whilst as to others (such as Nereites] no 

 certain conclusion can be arrived at. Upon the whole, it 

 would be safest to adopt Mr. Salter's proposal, and refer all 

 these remains provisionally to the artificial genus Helminthites , 



Fig. 93. Crossopodia Scotica, an Annelida track. Silurian. (After M'Coy.J 



retaining Scolithus for the burrows. As regards the distribu- 

 tion of these remains, it is sufficient to say that they occur 

 more or less abundantly in almost all strata of a suitable 

 mineral character from the Cambrian Rocks upwards. 



CHAPTER XIV. 



ARTHROPOD A. 



CRUSTACEA. 



DIVISION ARTHROPODA, or ARTICULATA. The members of 

 this division of the sub-kingdom Anmilosa are distinguished 

 from the preceding division of the Anarthropoda by the pos- 

 session of jointed appendages, articulated to the body. The body 

 is composed of a series of segments or "somites" arranged along a 

 longitudinal axis ; each segment occasionally, and some always, 

 being provided, at some period of life or other, with articulated 

 appendages. Both the segmented body and the articulated limbs 



