TURBINARL'E PELTIFORMES. 45 



are so. The columella (sometimes indistinct) irregularly oval, protuberant, granular, and 

 very solid looking. 



The interseptal loculi vary according to tlic character of the septa and cccncnchyma. 



The ccenenchyma is in section very dense. Tlie surface marking varies greatly, tlie 

 ridges are thick, granular, and very solid looking, or broken up into solid granules. 



The specimens associated under this name afford an excellent example of the amount 

 of variation which may occur in the character of the calicles. There are four, collected at the 

 same time, in the same place, and three of them growing exactly alike (the fourtli is only a 

 fragment), and yet in all four cases the calicles differ greatly in almost all exact characters. 

 The calicles agree only in the amount of protuberance, whereas in size of aperture, in degree 

 of cvowdincf, in number of septa, in sliape and depth of the fossa, and in distinctness of the 

 colunu'lla, no two are alike. While agreeing again in the density of the ca-nenchyma in 

 section, which is a mechanical necessity, owing to the horizontal growth of the thin coralluni. 

 they differ entirely in the characters of the surface markings. 



This case brings us face to face with the question, " which characters are most impoitant 

 in determining relationship, the method of growtli, or the shape of the individual calicles ?" 

 One would think it very unlikely that these specimens should owe the exact similarity of 

 their forms to the influence of the environment, which is never quite uniform over any large 

 area. The form depends upon the budding, i. e. upon processes somewhat withdrawn from 

 immediate contact with the surrounding medium. The polyps, on the other hand, which 

 determine the character of the calicle, are in constant and immediate contact with the external 

 world, and react to all the variations in the environment. 



r.ut there happen to be specimens of T. patula from the Torres Straits showing exactly 

 the same form of corallum, with the same eccentricity of the stalk, which proves that at least 

 in tins region the environment must exercise a powerful influence on the forms of the 

 coralla. In this case, then, all our characters break down. The only character uniting the 

 specimens appears to be due to the environment. There seems to be but one alternative to 

 the provisional classification here adopted, viz. to attempt to distribute the specimens under 

 otlier headings according to the characters of their calicles. In view of the enormous amount 

 of variation in the calicles on one and the same corallum, such a task appears from our present 

 standpoint almost superhuman {vide Introduction, p. 19.) 



The specific name is adopted from the generic name agaricia, the typical form of which 

 is not unlike that of these specimens. 



Tlie largest is 17 cm. in longest diameter, and is chosen as the type specimen. 



a-c. Torres Straits West. Trof. A. C. Haddon. 



d. (a fragment). Pi-of- A. C. Haddon. 



A very minute specimen, 1 cm. high and 2 cm. in diameter, and labelled tentatively 

 " T. brassicail) Dana," may perhaps belong here. It is decidedly peltate. But it is impossible 

 to say to which of the peltate species it belongs, or whether it is the young of an unknown 

 form. 



a. Habitat unknown. Lords of the Admiralty. 59. 2. 25. 7. 



