106 



THE GEOLOGIST. 



minutelv perforated * Exteriorly the surface is variously sculptured, aud 

 sparingly or closely covered with hollow tubular spines. It was also during 

 the deposition of i iie Carboniferous deposits that the gi-eatest number of species 

 and individuals prevailed, for as many as fifty species are said to occur ; but it 

 is not always easy to distinguish certain forms which may after all be but 

 varieties of some of the better determined or characterised species. It is very 

 desirable 1o see the complication of species disappear ; and when a single well 

 defined species is made to absorb one or half a dozen old and unrecognizable 

 ones, it is a favour to science ; and our constant efforts should tend to remove 

 useless names from the nomenclature, and seek the points of similarity with 

 (;ven more assiduity than the differences which we are prone to exaggerate in 

 tlie constant desi]-e to create new species. 



XXVL — Pkodtjctus gigajtteus.I Martin sp. PL v., figs. 1-4. 



Anomites giganteus. Martin, Petrif. Derb., pi. xv., fig. 1, 1809. 



Tliis shell varies somewhat in shape according to age and specimen, but is 

 nsually more or less transversely oval, and ddated at the sides. The hinge- 

 line is' straight, and generally exceeds in mdth the other portions of the sheU. 

 It usually possesses no hinge-area, but m some exceptional specimens there ex- 

 ists a ru(limentai7 one, especially in the ventral valve ; no teeth or sockets ever 

 existed for the regular articulating of the valves. The ventral valve is very 



uj^om-T.latJ.^''''''^^ ^' ^' ^^oodward; more detailed representations will be found 



Riiit PrnrTil,'!]-'^?."^''^^^^ ^ pertains to tlie species of Pi-oductus con- 



Bua 1 rol. do Koiunck s exceUont " Monogi-aphie des Gem-es Productus et Chonetes." Liege, 



hil .ShXlS^ " I^^a^^rglen and East Kilbride :" 1793. Page 316, in 



