218 



EVENINGS AT THE MICROSCOPE 



You perceive that there is a general similarity between 

 these transparent little creatures and the Zoea described 

 by Mr. Couch; but there are great differences in detail. 

 The glassy shield or carapace shoots out in front in a stiff, 

 inflexible, very fragile spine. This is perfectly straight, 

 and nearly thrice the length of the whole shield. It is 

 beset, on various lines on its surface, with short slender 

 spinules jointed to shoulder-like angles, and not serra- 

 tures. Its interior is perforated by a canal, which dilates 



ADULT SHORE-CRAB. 



and narrows irregularly. The carapace posteriorly is semi- 

 oval, projecting a transparent convex vault far over the 

 part where the abdomen is attached to it, as is seen when 

 the latter bends down. Its extremity gradually tapers 

 into two straight, sub- parallel, stiff spines, about as long 

 as the carapace itself, each terminating in a hooked point. 

 The abdomen ends in a spinous plate, which is very 

 elegantly lozenge-shaped, and beset with spines. Each of 

 the two latero- posterior edges of the lozenge is cut into 



