SPAESICAVEA. 
385 
Diagnosis. 
Zoariiun of thin, cylindi’ical branches, which divide dichoto- 
mously. The branches end bluntly, and have no narrow 
prolongation bare of apertui’es. The walls are ornamented 
by well-marked radial ribs, between which are numerous 
pores. In places where the apertures are crowded and occur 
in regular spirals, the radial ribbing is obscui’e. 
Peristomes highly raised, and ornamented by radial buttresses 
and ribs. The apertures are distant and irregularly scattered ; 
but in older parts of the zoarium they are close and aiTanged 
in regular spirals. 
Gonocyst a nodular or terminal expansion of the stem. 
Dimensions. 
Fide Pergens. 
Diameter of a branch ... • 75-1 -5 mm. 
Diameter of zooecia ... — ,, 
Diameter of aperture ... *08 ,, 
Distkibution. 
Form carantina. Form francqana. 
.. -7 mm. ... 1 mm. 
.. -2 „ ... -3 „ 
•06 ,, ... -08--1 „ 
British : 
Upper Chalk : Croydon ; Beachy Head ; Bromley ; Salisbury. 
Middle Chalk ; Chatham. 
Foreign : 
Danian : Faxoe. 
Senonian : Departement du Nord ; Arche de Leves, near Chartres. 
Coniacian : La Bibochere and Luynes, Indre-et-Loire. 
Turonian : Angouleme, Charente ; Villardin, Loir-et-Cher. 
Figuees. 
PI. XIII. Fig. 1. A branch of which the upper part shows the 
carantina and the lower francqana forms; X 10 dia. Middle 
Chalk: Chatham. Vine Coll. D. 695. 
PI. XIII. Fig. 2. A branch with the radial ribbing only 
faintly recognizable ; X 10 dia. Middle Chalk : Chatham. Vine 
Coll. D. 2623. 
PI. XIII. Fig. 3. A worn zoarium in which the wall with the 
maculae has been removed; X 10 dia. Middle Chalk: Chatham. 
Vine Coll. D. 698. 
PI. XIII. Fig. 4. A branch with the upper part rubbed down 
to show the maculae in cross section; X 10 dia. Middle Chalk: 
Chatham. Vine Coll. D. 721. 
PI. XIII. Fig. 5. A branch of the form francqana^ X 12 dia. 
Middle Chalk : Chatham. Gamble Coll. D. 4071. 
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