42 Clarence J. Elmore 



extending to the center, leaving no central space ; teeth fine, about 

 6 in 10 ju,. 



In Platte River, Grand Island ; Put-in Bay, pond on island in Lake Erie, 

 Ohio. 

 In San Joaquin River, Stockton, Cal. 



Family 2. CHAETOCERATACEAE 



Cells short, usually in filaments, cylindrical or flattened. Valves 

 alike, terminated by a hood, pointed with a bristle; or frustules 

 with valves unlike, mostly smooth ; furnished with awns, horns, 

 spines, or setae; often imperfectly siliceous; with a long central 

 spine. 



5. Chaetoceros 



Chaetoceros Ehr. in Ber. Bcrl. Akad., p. ig8. 1844. 



Bacteriastriini Shadb., 1853; Actiniscus Ehr., 1854. 



Etym., Gr. x"-^'^V> bristle, and /cc'pas, horn, referring to the long 

 awns. 



Valves convex, elliptic or circular with very long awns ; cells 

 usually united in long cylindrical filaments. 



Chaetoceros elmorei Boyer, A New Diatom, in Proceedings of The 

 Academy of Natural Sciences of PliiladelpJiia, p. 210. 

 March, 19 14. 

 PI. I, figs. 27-33. 



Filaments straight, 23^1* wide. Cells rectangular with sharp 

 angles ; valves slightly convex ; foramina narrowly linear, irregu- 

 lar, bipartate. Setae straight, hollow, approaching each other at 

 an acute angle and crossing at a right angle near the corners of the 

 valves, about ten times the length of the valve. In valve view they 

 diverge from each other at an angle of about 80°. Terminal setae 

 shorter than the others, somewhat curved in the direction of the 

 filament. Spores with the primary valve arcuate, secondary valve 

 produced into a subconical frustum. Rarely in free spores the 

 primary valve is covered with minute spines. The valves are 

 joined together near one side by a tubular commissure, from six- 

 tenths to eight-tenths of a micron in thickness, situated near the 

 edge of the valve, usually at unequal distances from each end, and. 



