160 



PAL*ONTOL0OY OF NEW-YORK. 



554. 2. CLATHROPORA FRONDOSA (n. sp.)'. 



Pl. XL B. Fig. 5 a - «. 



Frond reticulate, expanded, flabellate, or funnel-shaped ; the two surfaces regularly and 

 equally celluliferous ; cells with rhoraboidal or oblong quadrangular apertures opening obliquely 

 upward ; tubular cells reaching to the centre, and gradually enlarging towards the aperture. 



This species consists of a thin expanded frond, produced by the anastomosing of broad flat- 

 tened branches. It appears more like a perforated flabellate frond, than a reticulate structure. 

 It has the general appearance of Retepora, from which it is not readily distinguished unless 

 both sides are examined. The form of the apertures of the cells, however, is more quadrangular 

 than in any species of Retepora I have seen, and this character may be of service in de- 

 ciding the reference of specimens. It usually occurs in the soft shale, one side adhering to the 

 stone, from which it is necessary to remove some portions of the coral before its real character 

 can be ascertained. Portions of fronds, six inches or more in diameter in every direction, have 

 been obtained, and which are imperfect on all sides, showing that the coral attained a large 

 size. 



From the mode of divergence of the frond from a centre, it appears that the perforations are 

 arranged in concentric circles, each row or circle having successively been at the outer margin 

 of the frond. 



Fig. 5 a. A fragment from a much larger frond. 



Fig. 5 ft. A small fragment where the perforations are smaller, though the coral does not ap- 

 parently differ in other respects from the preceding. 



Fig. 5 c. An enlarged portion of the surface, showing the arrangement of cells in reference to 

 the perforations. 



Fig. 5 d. An enlargement where the cells are arranged in series parallel to the aiis of the 

 branch. 



Fig. 5 e. A section of a branch enlarged, showing arrangement and upward divergence of the 

 cells. 



Position and locality. In the shale of the group at Lockport, and very rarely in the lower ' 

 part of the limestone. Macerated fragments sometimes occur associated with Callopora and 



TrEMATOPORA. (Collection of Col. Jewett.) 



555. 5. RETEPORA DIFFUSA. 



PL. XL C. Fig. la-f. 



Fruticulose ; several stems originating from a common base ; stems frequently bifurcating 

 and spreading laterally, forming a broad frond ; stems and branches celluliferous on one side 

 only, the other side deeply striated longitudinally ; apertures of cells quadrangular or sub- 

 rhomboidal, with the angles in the direction of the longitudinal and transverse axes of the stems 

 and branches, and sometimes much extended longitudinally ; branches often crowded and 

 tortuous J terminations often thickened or clavate, and always obtuse. 



