VOL. 2] Kofoid.—On Heterodinium. 351 
Euheterodinium subgen. nev. 
Epitheea dorso-ventrally compressed, with straight, convex 
or concave sloping lateral margins which are usually thickened 
and have doubled ridges between the lateral margins of the 
apical plates. Antapical horns well developed. Girdle not very 
oblique. 
1. Epitheca with strongly convex sides, apex broadly rounded _.... 
ee Ae Sat Neeson eae ore sea ane asec eats eect ten ES ANOEG UAE 
1. Epitheca with straight or concave sides, apex not broadly rounded... 2 
2. Epitheca low, its altitude about one-half the transdiameter -............ 
Be Pattie = Maen gn 8 Mes Rn dasa nee ides sect s eomaswtae ean aet kesh Ate edad H. rigdenae 
2. Epitheca high, tapering, nearly equal to the transdiameter _............ 3 
3h TUGHE Gale gonkel lomut wince Neel eae ae ae ce eee H. trirostre 
See Wehteambant cele no tbc cate Cee terpenes ee ea ee eet ee ee ee 4 
4. Reticulations very coarse, scantily developed H. leiorhynchum 
4. Reticulations subregular, very delicate ..............-..--.-- H. blackmani 
4. Reticulations medium sized, very heavy _.....................- H. hindmarchi 
Platydinium subgen. nov. 
Epitheca dorso-ventrally compressed and hollowed out ven- 
trally, scoop-shaped. Lateral margins convex, not contracted to 
an apical horn. Girdle very oblique dorso-ventrally. Antapieal 
horns present. 
i, A\ratigyjorioal Innes): CWNAETAO ENING 5 eee cee eee eee H. scrippsi 
He A\inireyanicewll INOS; COMET ECG oe see occas ee cere H. whittingae 
Heterodinium sphaeroideum sp. nov. 
Pl. 3, fig. 15. 
A minute symmetrical species of spheroidal form without 
apical or antapical horns. The body is spheroidal or broadly 
ellipsoidal, the length 1.1 transdiameters. Dorso-ventral diam- 
eter equal to transdiameter. Epitheca a low dome, its altitude 
0.4 transdiameters. Hypotheca exceeding the epitheea, elon- 
gated hemispherical, its altitude 0.6 transdiameters, with broadly 
rounded symmetrical antapex. Girdle premedian, transverse 
furrow indented, posterodexiotropic with very slight displace- 
ment scarcely 0.2 its width, its anterior and posterior lists equal 
