DESCRIPTION OF CHALK CORALS. 269 
consequence apparently of external additions. The best-preserved apertures 
were slightly inclined upwards and had a raised margin. The tubular nature 
of the lateral structure was shown (fig. 40) partly by an opaque-white, narrow, 
irregular band, bounded outwardly by a translucent line similar to those forming 
the sides of the abdominal cavities ; and partly by abraded branches presenting 
on each side a narrow furrow more or less filled with chalk, when first exposed ; 
and it is believed that the similarity in the surface colour of both the central 
tube and the band was owing to infiltered matter: at the extremity of a branch 
occurred also two minute openings, which accorded in position with the tubuli 
of the band. 
The coral represented by figures 41 and 41 a to c, agreed more nearly than the 
preceding in its mode of growth with M. De Blainville’s delineation of Al. ramea. 
If examined without a knowledge of the specimen above noticed, some of its cha- 
racters might escape detection, and specific differences be assumed ; the whole 
of the ramifications exhibiting under an ordinary pocket lens a semi-cylindrical 
outline and uniform composition. An attentive inspection, however, proved the 
existence of a central tube with lateral inclined bands of an opaque white colour, 
and separated from the medial cavity by very fine translucent lines ; while frac- 
tured portions (figs. 41 0, c) displayed side furrows and pores, which could not 
readily be considered as direct precursors to a bifurcation. 
How far a smooth subsurface or other local causes may have influenced dif- 
ferent states of development or relative perfectability, the examination of only 
two specimens afforded no grounds for a satisfactory inference ; but so far as 
observed the composition was similar in each case; and therefore it has been 
deemed correct not to separate, at present, the two fossils specifically. 
Alecto gracilis, Milne-Edwards. (Tab. XVIII. A. figs. 1, 1 a, 1b, 1c.) 
Ramifications irregular, dichotomous or issuing laterally, breadth variable, 
abdominal tubes essentially uniserial ; position of apertures not central, more or 
less alternately inclined to the right and left, form oval, margin slightly projecting. 
Milne-Edwards, Ann. Sc. Nat., 2nde série, Zool. tome ix. pl. 16. fig. 2, 2 a, or 
Recherches sur les Polypes, Mém. sur les Crisies, &c. p. 15. Chalk of Meudon. 
Norfolk chalk, Woodward in Morris’s Cat. Brit. Foss. p. 30. 
The coral (fig. 1) believed to be rightly referred to Alecto gracilis displayed 
no proofs of lateral structures. It was attached to a Micraster, and exhibited 
many signs of irregularity of development, some of which might be ascribed to 
2N 
