l86 AQUATIC MICROSCOPY FOR BEGINNERS. 



d. Spines eight, in two longitudinal rows of three 

 each, with one anterior and one posterior cen- 

 tral spine, octondrius, 8. 



d. Spines in two transverse rows, not projecting be- 

 yond the ends of the central prolongations, 

 spindsulus, 9. 



d. Spines in two transverse, highly-arching rows, 

 the posterior longest and projecting beyond the 

 ends of the caudal prolongations, longispindsus, 

 10. 



1. Ch^t6\otus i.oricAtus (Fig. 137). 



The scales on the back and sides are aranged in im- 

 bricated rows, ^he convex free margins 

 being directed forward. Although so 

 completely covered, the body is very 

 flexible, the scales freely sliding over 

 each other when the animal curves to 

 one side. The mouth is obliquely 

 placed, as may be seen when the Chse- 

 tonotus is viewed in profile, and its 

 internal margin is strongly beaded. 

 The eggs are armed by hollow pap- 

 illae, or by short hollow spines whose 

 summits are bifid or emarginate. 



Fig. 137. — Chaetonotus 

 loricdtus. 



2. Ch^t6notus mAximus. 



The back and sides are covered with spines which 

 are often rather longer on the posterior region than 

 elsewhere. They are arranged in longitudinal parallel 

 rows, yet they often seem to be irregularly scattered, 

 so that the' animal presents an untidy, disheveled, 

 and disreputable appearance. The spines are min- 



