FROM THE OOLITIC STRATA. 21 



Genus nov. — Gonioseris. 



The corallum is simple and free. 



The base is polygonal in outline and the projecting angles are formed by groups of 

 cost^ terminating in septa. Between the angles the margin is concave externally. The 

 centre of the base is concave. 



The costas are numerous and they cover the base. Many converge at each angle 

 along a line leading from the large septum to the centre. 



The upper surface of the corallum is convex, and is divided by masses of septa which 

 are continuous with the angles of the base, and which, after projecting there, become 

 exsert and pass to the axial space where they meet. 



There is a large, prominent, primary septum in each mass. 



The calicular wall is invisible. The synapticulse are broad and numerous. 



This extraordinary genus is represented by two forms in the Inferior Oolite. Probably 

 the normal number of projecting angles is six, but in one specimen there are five, and a 

 careful examination of it tends to prove that there was no abortion of a septum, but that 

 the quinary arrangement was initiated from the first. 



The type is Gonioseris angulata nobis. Probably the small specimen delineated in the 

 same plate is a young form of it. Plate VII, figs. 10 — 11. The third specimen I have 

 called Gonioseris Leckenhyi after the discoverer of these fossils. 



1. Gonioseris angulata, Duncan. PI. VII, figs. 1 — 5. 



The base is hexagonal, and the projecting angles are connected by marginal concavities. 

 The space between the central concavity of the base and the margin is broad and slightly 

 convex. 



The costse are of two kinds — those which pass from the concave margins to the 

 concavity of the base, and those which pass from the margin near the angles to a line 

 directed from the angle to the base. All the costae are thin, slightly crenulate, alternately 

 large and small ; and they are all continuous with the septa. Each septal mass, which 

 forms one of the six angles, consists of a large primary septum and several small septa 

 associated on either side. The mass projects upwards and outwards from the base, 

 and then curves inwards and slightly upwards to the axial space. The spaces between 

 the six masses are convex from within outwards and concave from side to side. 



There are six large primary septa ; and the others are subequal, long, thin, crenulate, 

 and unitinsr. 



