UNKNOWN ATLANTIC OR WEST INDIAN PORITES. 81 



thus made at the beginning of my apprenticeship to this difficult group, and consequently before 

 the results obtained during the preparations of Vols. IV. and V. were available. Still, inas- 

 much as they are illustrated by photographs taken for the purpose in the Paris Museum 

 under the express direction and supervision of Dr. Charles Gravier, they are sufficiently near 

 to be able to support the serious arguments which I have here Ijased upon them. 



66. Porites West Indies x. 1. (P. Americana inccrtm scdix prima.) 

 Syn. Madrepora Porites Solander, Zooph. (1786) p. 172, pi. xlvii. fig. 1. 



Description. — The corallum rises in stout stems which appear to swell, flatten slightly, 

 and then either fork at right angles, or else lireak up into clusters of nearly spherical knobs of 

 different sizes. The living layer appears to extend about 6 cm. 



The calicles are neatly polygonal. The walls very thin, incompletely and slightly zigzag. 

 The septa, of irregular lengths and roughened, project freely into the fossa, that is without 

 any union with pali, or columellar tangle. The pali are represented as a ring of small 

 points, with a still smaller columellar tubercle at the centre. 



This description is based upon Ellis and Solander's well known figure. Its interest is not 

 only historical, inasmuch as Lamarck referred to it as specifically identical with the specimen 

 which he called P. clavaria, but actual. The growth-form is peculiar. It has all the 

 aspect of being a West Indian form, but the forking is very ii-regular, and entirely unlike 

 that of Lamarck's own P. clavaria, the forking of which is neat and orderly, see fig. 1 (PL XIIL). 

 This marked difference between the growth-forms of the two was apparent to Duchassaing 

 and Michelotti, who in their Mem. sur les Cor. des Antilles called it P. Solanderi, and identified 

 it with a form they had found at St. Thomas (see p. 57) ; but this latter identification was 

 dropped in the Supplement to that treatise, which appeared in 1864. 



The illustration of the calicles, though too superficial, yet shows a type which ought to 

 be recognisable again. Nevertheless we rely mainly upon the growth-form for its recognition. 

 This latter is remarkable enough, and unlike that of any other West Indian Porites I have 

 seen, either as an actual, or as a figured specimen. If it is a normal form, our only 

 chance of finding its relationships is when collections are again made from its proper 

 locality. If it is abnormal, it will be of very little future use for the building up of our 

 knowledge of the group. 



67. Porites West Indies x. 2. {P. Americana inccrtw sedis sccunda.) (PI. XIII. fig. 1.) 



[Paris Museum.] 



Syn. Porites clavarm Lamarck, Animaux sans Vertebras, ii. (1816) p. 270. 



Description. — The corallum rises as a stout cylindrical stem, which forks regularly and 

 dichotomously at about every 2 cm. apart and at a wide angle, but showing a tendency for 

 the prongs to bend up into the vertical. The stems and branches are all of nearly uniform 



M 



