OF THE THIRD TANGANYIKA EXPEDITION. 189 
Tanganyika.—In plankton, Komba Вау (11 Oct. 1904; no. 135) and near 
Kala (19 Nov. 1904 ; по. 170). 
This variety differs from the typical form in the presence of the spines at 
the posterior margin, in the conical apical part of the cell, and in the absence 
of the small papilla which cover the sutures between the plates in the typical 
form. 
Genus PERIDINIOPSIS, Lemm. 
311. PERIDINIOPSIS CuxNINGTONIL, Lemm., sp. n. (Pl. 9. fig. 2.) 
Р. paullo longius quam latius, 315-38 р longam et 21—31:5 и latum, margine 
posteriore truncato; corpore in partibus inzequalibus duabus a fossa transversa 
diviso, parte apicali majori; fossa transversa (PI. 9. fig. 2, a) conspicue spiraliter 
disposita; fossa longitudinali in partem apicalem extensa et margine posteriore 
versus valde dilatato. Membrana delicatissime reticulata; striis intercalaribus 
delicatis. 
Epivalva (Pl. 9. fig. 2, d) conica, cum tabulis sequatoriis 6; tabula rhom- 
boidea apicem extensa; tabulis apiealibus 4, ventralibus 2 et dorsalibus 2. 
Hypovalva (Pl. 9. fig. 2,e) truncato-conica, cum tabulis sequatoriis 5, ven- 
tralibus 2 et lateralibus 2 cum spina robusta brevi singula; tabulis 
antapicalibus 2, cum spina singula in tabula unaquaque. 
Tanganyika.—In plankton, Komba Вау (11 Oct. 1904 ; no. 135), and near 
Kala (19 Nov. 1904 ; no. 170). 
The body of this species resembles that of Peridinium quadridens, Stein, 
but differs in the number and arrangement of the plates and in the number 
of the spines. | 
This is the second described species of the genus Peridiniopsis. P. Borgei, 
Lemm. (in Arch. Bot. K. Sv. Vet.-Akad., Bd. ii. (1904) no. 2, p. 134, t. 1. 
figs. 1-5), has three antapical plates and no spines, whereas P. Cunningtonii 
has two antapical plates and six conspicuous spines. In both species the 
epivalve possesses six equatorial plates. 
Genus CERATIUM, Schrank. 
279. CERATIUM HincNDINELLA, О. F. Müll. 
Small forms with only two antapical horns: length 136-148 р; breadth 
50-54 u ; length of apical horn about 50-60 ш ; length of 1st antapical horn 
about 30-44 u ; length of 2nd antapical horn about 10-12 д. (РІ. 9. fig. 4.) 
Victoria Nyanza.—In plankton, near Bukoba (21 Apr. 1905; no. 252). 
The species was very scarce, and the few specimens observed differed very 
much from any others which have come under my notice. They were small, 
with short horns, and the wall was strongly reticulated. The apical horn 
was short with a broad base and slightly curved, and only two antapical 
horns were present. The first antapical horn was attenuated from a broad 
base, apiculate at the extremity and turned inwards. The second antapical 
