igo 



AQUATIC MICROSCOPY FOR. BEGINNERS. 



base, so that the animal is almost completely clothed 

 in an armor composed of these basal enlargements. 



7. Ch^t6notus en6rmis (Fig. 141). 



The upper and lateral surfaces of the head and neck 

 are clothed with short, recurved prickles, which also 

 extend along the ventro-lateral margins. The central 

 and posterior parts of the back bear thirteen posteri- 

 orly directed, but only slightly curved, spines 

 arranged in transverse rows, with three in the first 

 row, four in the next following, two widely separated 

 in the third, three in the fourth, while the fifth series 

 consists of a single centrally located one. On each 

 side near the posterior margin are two long, conspicu- 

 ous, and recurved thorns, apparently belonging to 

 the series of small spines fringing the lateral body- 

 margins. 



Fig. 141 — Chaet6notus 

 endrmis. 



Fig. 14a. — Cha3t6notus 

 spih6aulus. 



Fig. T43. — Chaetfinotui 

 longispindsus. 



8. Ch/et6notus octonArius. 

 This is a small, active form, readily recognizable by 

 the arrangement of the recurved dorsal spines. These 



