112 MADREPORARIA. 



straight (i.e. not wavy) ; that the septa, whose edges are granulated, occasionally meet ; that 

 pali were represented ; and that the interseptal loculi were large, open and well developed 

 between the straight septa. 



This seems to be a true Porites in spite of the fact that the figure shows fifteen septa. 

 The description states that there were twelve. 



Group IX.— FORMS FROM NO RECORDED LOCALITY. 



In Group VII. (p. 80) descriptions were given of Porites as to which there was good reason 

 to believe, either from their structural details or from their labels, that they were from the 

 West Indian and Atlantic region. But in this group will be found those which show no 

 such satisfactory sign. Indeed, as far as I can yet judge, the majority of them have the 

 appearance of belonging to the Indo-Pacific area. A few doubtful cases are, however, noted. 



103. Porites z. 1. (P. incertce sedis prima.') 

 Syn. P. arenosa Esper, Fortsetzung, i. (1797) p. 80, pi. bcv. 



Description. — The corallum is encrusting, as a thin, smooth, explanate stock, with edges 

 hardly 4 mm. thick. 



The calicles are ill-defined, slightly sunk, with loose, open, reticular walls, " the meshes 

 taking almost more room than the solid matter." The interseptal loculi run back freely into 

 the reticular walls. The septa are represented by rows of sand-like granules. The pali are 

 scattered and not arranged in any distinct ring. The columellar tubercle is occasionally 

 present. 



The unbleached stock is a pale yellow-ochre. 



This description and Esper's figure embody all that we know about this Porites. On the 

 other hand, the amount which has been written about the " species " arenosa, and the number 

 of quite different Porites which have been identified with it is positively ludicrous. As 

 a specimen it represented a solid fact. As a " species " it has been a trap into which almost 

 every student of the Porites has fallen. I believe that in every collection of any size in 

 Europe, one or more Porites, often very unlike one another, will be found labelled arenosa. In 

 the first draft of this Catalogue I attempted to give some account of the way it has imposed 

 upon worker after worker, and I penned several pages in an attempt to unravel the confusion ; 

 but in this revision I decided to state the bare fact alone, cautioning all students for the future 

 to ignore the so-called " species " and confine himself simply to ascertainable fact. 



