192 



AQUATIC MICROSCOPY FOR BEGINNERS. 



Fig. 144 — Lepidod^rma rhomboides. 



and by the remarkably long and jointed caudal 

 branches, each of the latter forming from . one-third to 

 one-fourth of the entire length of the body. The 



animal is the largest of the 

 group, yet discovered, 

 measuring -^ inch long. 

 The caudal branches are 

 composed of about twenty 

 sections or joints, each of 

 which is slightly constric- 

 ted. The head is broadly 

 rounded, and formed of 

 three lobes, one frontal and two lateral, the former 

 terminating on each side in a single, acuminate, hook- 

 like process, habitually in close apposition with the 

 anterior region of the lateral lobes, of which the pos- 

 terior extremities also terminate each in a single 

 hook-like continuation, rather more conspicuous than 

 those at the front. The mouth is beaded, and has im- 

 mediately behind it on the ventral surface a deep, 

 narrow, transverse, and slit-like depression, rather 

 less than one-half as long as the diameter of that part 

 of the head. This is a problematical feature. 



The bac'i and sides are completely clothed by mi- 

 nute, imbricated, rhombic scales, their front pointed- 

 margins being directed towards the head. They are 

 not more than -j^Jj-j- inch in length, and when examined 

 with a high power (one thousand diameters) they 

 present a beautiful appearance. The lateral margins 

 then seem to be thickened, and the posterior border of 

 each scale appears to bear a minute supplementary 

 scale in the shape of a triangle. The margins are 

 sometimes convex. 



