ISO!.] MICROSCOPICAL JOURNAL. 101 



stalk. Podocystis is pear-shaped with a middle line. The valve of 

 Pyxidicula is circular and very convex. Tryhliotiella has a heavy 

 inner marii;iiial line. Rap/ioneisVavs ends produced. 



In the fourth, if the frustiileis wedge-shaped it is Lionophora^ Fodos- 

 pheti/a, Rhipidophora or Clirnacosphenia. 



The frustules of the first form a fan ; the single frustule of the third, 

 with its long stalk, resembles a battledoor ; Climacosphenia has com- 

 partments ; Podosphenia lias the ends indented, but no long stalk, and 

 the frustules are not united. If the heavy lines are not arched l)ut straight 

 it is Striatella^ RJiabdoncina ^ or Grammatophora. Interrupted lines 

 will make it the second, frustules in a zig/ag chain the third. Ananlus 

 has indentations at the sides which show in either view. 



And in tlie last division Chcctoceros has valves with two long spines 

 or threads ; RJilzoselenia very long valves with conical ends tipped 

 with a spine ; Syndendrizim ^sevexixX spines on one valve only ; Syringi- 

 din7n, valves unlike and two horns on one valve, one on the other. 

 The frustule of /?////;^^'rt: is a rhomboid or trapezoid ; Xhsiio^ J^iddulphta 

 and Amphitetras is quadrilateral, but the latter is flat, the former in- 

 flated. If the valve is triangular it is Tricei-atiutn^ but Priccratliifn 

 is sometimes quadrangular or even pentagonal. It is therefore hard at 

 times to distinguish Priccrathim from Arnphitctras. The angles of 

 7'riccrathim oftfcn have short horns or little teeth which may serve as a 

 guide, and the frustules of Aviphitctras form a zigzag chain. 



Here, then, is an easy way of becoming acquainted in turn with the 

 principal fresh-water fossil and marine forms of .<ome 84 out of about 

 1 10 genera mentioned by the Micrographics which, together with Mac- 

 donald's work on Water Analysis, I have taken as my guide, arranging 

 the genera, however, somewhat differently, and picking out simply the 

 salient points, for some of which I have also consulted Carpenter and 

 \VV>lle's work. 



\To be continued. \ 



Microscopy for Amatems. 



ByT. charters white, 



gllEKETT CLUB. 



\ Continued from page 9/.] 



Marine Objects. — No fiekl of research so abounds in objects worthy 

 of attention as the sea-side, and here the student may make himself famil- 

 iar with marine fauna and flora to any extent, for the rocks and the algie 

 will furnish him with a variety of diatoms to be studied in their living- 

 state, while on a calm warm day the surface of the sea will be found 

 teeming with the embryonic forms of many of the Crustacea. The 

 rock caverns at spring tides will well repay the search tor diflerent 

 kinds of sponges, and various species of the Ascidia. The collecting 

 kit of the pond-hunter will suffice for many localities. In the rock 

 pools, deep down, he will find treasures in the shape of forests of liv- 

 ing Polyzoa^ whose feathery forms he will soon learn to distinguish. 

 If these are attached to loose fragments of rock or pebble, they may 

 be transferred bodily to a jar of clean sea water, and will there live 



