^38 STRATIGRAPHY 



species from those shown in Slides 70, 121, &c. The specimen is too fragmentary 

 for identification. It may perha23s be allied to A. dissepimentalis. (Taylor, op. cit., 

 Plate IX., photo 53.) 



Plate LXXVIII. Fig. 1. Portion of outer wall cut somewhat obliquely and 

 showing one septum. The thick wall and pores are characteristic. Plate XV. 

 (Bornemann) shows* a similar feature in A. spatiosus (Plate LXXVI. Fig. 4 

 sketched herewith), and this may tentatively be allied therewith. . 



Plate LXXVIII. Fig. 2. Portion of the inner wall of a regular Archceocyatlms. 

 It is cut transversely, and shows large mural pores and fragments of septa. The 

 fragments remind one of the section of A. ajax shown hi photo 18 on Plate IV. of 

 my Memoir, but it is obviously impossible to draw any conclusions as to species. 



Plate LXXVIII. Fig. 3. The figure shows a vertical section through one-half of 

 an Archceocyathin(v cup. It belongs to the Protopharetra division of the class, for 

 the intervallum is crossed by an irregular meshwork and not by regular septa. On 

 the left is the outer wall, which is evidently rugged and denticulate. The septal 

 network connects the outer wall to the inner wall. A portion of the latter (at the 

 top on the right) appears to be cut parallel to its surface. This wall is here seen 

 to be perforated by rows of small pores — about four to a millimetre, a very common 

 distribution. It is perhaps akin to P. radiata (Bornemann) ; for the intervallum 

 seems too narrow for P. rete (Taylor), and the meshwork is rather more regular. It 

 is, of cour.se, impossible to identify it without a cross-section, which might ally it 

 with Dictyocyathus. 



In Plate LXXVI. Fig. 5 is reproduced a figure of Bornemann's (op. cit., Plate 

 XIX. Fig. 7), which shows how the organism would appear if it were complete. In 

 the Antarctic specimen only the left half of the section is present. 



Plate LXXVIII. Fig. 4. This appears to be a section of one-half of a cup, which 

 differs considerably from any so far recorded. The structure on the right, appearing 

 as a dark, dense, u'regular zone, is most probably a section of the outer wall. Then 

 occurs a zone of u-regular reticulate material, which occupies, I believe, the intervallum ; 

 and on the left is a row of large, regular meshes, which represents the inner wall. 



This conjectured explanation will be seen to have points of resemblance to several 

 ArchcBocyathincB, notably A. retezona ((Taylor, op. cit., p. 121) and Ethmophyllum 

 dentatum (Taylor, op), cit., p. 130). But the latter have very regular septa, which 

 are certainly not present in this specimen. In its sejstation it agrees with Proto- 

 pha,retra, but none of the latter have the regular meshed structure shown on the left 

 of the photo. 



It may be provisionally termed Protop>haretra retezona, but further material is 

 requii-ed for a complete description. 



Descrip)tion of Species. General form unknown ; probably cylindrical, like most 

 Protopharetrce. Outer wall dense and irregular. Septa rejiresented by an irregular 

 * Veistein. Cambrisclien Schichtensyst. Sardinien, 1866, t. 15, f. 2. 



