Prof. E. Forbes on Fossil Invertehrata from Southern India. 159 



will be rendered unintelligible to all but those minutely acquainted with specific 

 zoology and botany. As the giving a name to a group at all is merely an arrange- 

 ment of convenience — since a numerical sign or a letter would serve all purposes 

 for the student in his closet — the extreme multiplication of names converts the 

 practice into an abuse, and tends to mystify and confuse the science. On the 

 equal value of generic terms, the value of natural-history statistics, whether as 

 serving to elucidate the modifications of form or structure in the animal or vege- 

 table series, or as furnishing data for working out the equally important subject of 

 distribution in time and space, must depend. Genera therefore should not, it 

 seems to me, be founded without deliberate consideration, full knowledge, and an 

 earnest conviction of the organic importance of the characters on which we base a 

 new genus. Neither genus nor species should be admitted which has not been or 

 may not be clearly defined in words ; and in the case of the former, if not of the 

 latter also, strong objections might be offered to the employment of merely com- 

 parative characters alone. 



The arrangements of the ambulacra already mentioned, the absence of a dorsal 

 impression, which indicates pecuharities in the arrangement and form of the 

 animal's burying-organs (its spines), taken in conjunction with a peculiar habit, 

 recognisable at a glance, are all organic characters of sufficient importance to 

 warrant the constitution of the genus Holaster ; and their value is borne out by 

 the peculiar distribution of this genus (now extinct) in time, all its species but one 

 being concentrated, as it were, in the Cretaceous epoch. 



1. Holaster indicus, sp. nov. PI. XIX. fig. 4. a, h. 



H. cordatus, inflatus, postice altior, extremitate anali obtuse rostrata, infra spatio post-orali 

 convexa, subcarinata. 



Length ly^^ inch. Breadth li inch. Greatest height 1 inch. 



Very regularly heart-shaped, nearly as broad as long. Back most convex pos- 

 teriorly in the space between the two postero-lateral ambulacra. Behind the 

 highest part the body contracts a little as if pinched in, and is narrowly truncated 

 at the anal extremity. The anterior extremity is deeply cordate. The series of 

 pores forming the ambulacra gently diverge, and almost all nearly equally. In 

 each series of the four dorsal ambulacra there are about twenty-four pairs of open 

 pores, the last five being placed distant from each other. The pairs of the several 

 series are not connected by grooves. The anal area is vertically oblong. On the 

 under-surface the most prominent part is the post-oral space, which is oblong, very 

 convex, and has a tendency to carination. The antero-lateral portions (cheeks) 

 are rather tumid. 



The nearest allies of this species are the Holaster sub orbicularis from the upper 



y2 



