for the Microscope. 41 



ttfisted. It differs from the next in being larger, and the 

 extremities obtuse. This occurs in brackish water. 



292. WEST'S NAVICULA (Navicula Westii}. In this 

 species the middle line is slightly waved or flexuose, and 

 the extremities somewhat acutely pointed . It is also found 

 in brackish water. (PL IV., fig. 37.) 



293. ELEGANT NAVICULA (Navicula elegans). The 

 valves are broadly spear-shaped, with slightly pointed 

 ends. The striae are curved and radiant towards the 

 smooth space around the central nodule. It occurs in 

 brackish water and tide-pools. 



294. LYRATE NAVICULA (Navicula lyrd). The valves 

 in this species are elliptic, marked by two narrow longi- 

 tudinal blank spaces, connected by the central nodule 

 into the form of a lyre : hence its name. Is found in sand 

 ripples. 



295. GRANULATED NAVICULA (Navicula granulata), 

 In this species the valves are broadly linear, with straight 

 sides, and the ends suddenly constricted to a point. It 

 resembles the next in outline, but differs in the coarseness 

 of the markings, which are large and brilliant. Nearly 

 opaque when dry. Also in sand ripples. 



296. CRYSTAL NAVICULA (Navicula humerosa). As 

 already observed, the outline of this species is the same 

 as the last ; but the striag are closer and less distinct, clear 

 and glassy when dry. Both species are common in sand 

 ripples. 



297. NARROW PINNULARIA (Pinnularia peregrina). 

 This genus differs from Navicula chiefly in the valves 

 being ribbed instead of striated. Under a high power 

 the ribs are found to be transversely striate. The present 

 species has narrowly spear-shaped (lanceolate) valves, 

 which gradually taper towards each extremity. Found in 

 brackish water. 



298. DISTANT-RIBBED PINNULARIA (Pinnularia distans). 

 The valves in this species are spear-shaped (lanceolate), 

 with distant radiating ribs, not reaching the central line. 

 It is a very common form in deep-sea dredgings. 



299. SALT MARSH STAURONEIS (Stauroneis salina}. 



