400 Mr. W. D. Lang—Revision of the 
2. P. bicornis, sp. n. 
Type-specimen. British Museum, D. 24388 ; cortestudi- 
narium-zone ; Luton, S.E. of Chatham, Kent. 
3. P. arrecta, sp. 0. 
Ty pe-specimen. British Museum, D. 8184; coranguinum- 
zone ; Gillingham, N.E. of Chatham, Kent. 
IV. Drancopora, gen. nov. 
Genotype. D. ancora, sp. n. Type-specimen. British 
_ Museum, D. 4035 ; Lower Senonian ; Chatham, Keat. 
V. DicrratTopoRa, gen. nov. 
Genotype. D. bivia, sp. n. . Type-specimen. British 
Museum, D. 24534; coranguinum-zone; Gillingham, N.E. 
of Chatham, Kent. 
b. Disuetoporry#, subfam. nov. 
Tabular Diagnoses of the Genera. 
A. Intraterminal front wall more arched; less 
secondary tissue; no secondary aperture...... I. Dishelopora. 
B. Intraterminal front wall flatter; much secondary 
intercecial tissue; a secondary aperture formed 
by a general prolongation of the apertural bar 
AS e PrOXiMAalShiGld yA cis ceiere apete setae reeys II. Geisopora. 
I. DisHELopPoRA, gen. nov. 
Genotype. D. bicuspis. 
Tabular Diagnoses of the Species. 
A. Apertural bar not specially differentiated ; 
length about 3 mm. 
I. Costee 20-30; unilaminar, incrusting...... 1. D. euckmerensis. 
II. Coste 16-20; unilaminar, incrusting .... 2. D. bispinosa. 
B. Apertural bar with broad median process ; 
cost 16-20; length 3-3 mm.; unilaminar, 
INCTUSUNE S Cacraenontae oe eee 3. D. valvata, 
C. Apertural bar with narrow median projection ; 
unilaminar, incrusting. 
I. Coste 10-15; length about 2mm......... 4. D. elaviceps. 
II. Coste 16-20; length nearly 1 mm. ...... 5. D. bicuspis. 
D. Apertural bar much flattened and proximally 
bent, with no obvious spine or crest; costee 
12-16 or more; unilaminar, incrusting. 
I, Length about 3mm: 2. Sacha oe ne 6. D. binoculata. 
II, Length about 1 mm. ..,..... 7. D. biforis. 
