﻿STROPHOMENA. , H9 



by the hasty fabrication of a number of new genera on half worked-out material and 



ideas. 1 



Palaeontologists appear to have generally agreed as to the propriety of maintaining the 

 two families above mentioned, but it is still uncertain whether the characters by which they 

 have been distinguished are of the importance at one time imagined. It was once sup- 

 posed that external spines were peculiar to the Produclidce, and always absent in the 

 Strophomenida ; but it is now well known that certain species of Orthisweve as thickly 

 covered with short slender spines as any of the Produclidce — e. g., P. punctatus. In external 

 shape also many Strophomenida differ but little from certain Productida, but interiorly 

 the absence of the so-termed reniform impressions in all the Strophomenida hitherto dis- 

 covered would appear to be the most constant character by which the two families can be 

 distinguished. 



In the Strophomenida, as well as in the Productida, no very prominent calcified pro- 

 cesses have been hitherto detected, for the support of those beautifully fringed appendages 

 which exist on either side of the mouth of the animal, and to which the (improper) desig- 

 nation of "oral arms," or "brachial appendages/' has been given by the greater number 

 of naturalists, and which are now believed to have subserved at once the function of gills 

 and of sustentation, and to prove which, as observed by Mr. Hancock, " it is only necessary 

 to refer to the manner in which the blood circles round the arms, and is carried to the 

 cirri, but more particularly to its circulating through these latter organs, and to return 

 direct from them to the heart," 



Genus STROPHOMENA, Rafnesque, 1820. 



Of this genus but a single species is known from the British Carboniferous 

 strata, viz.: 



Strophomkna ruomboidalis, Wahlenberg, Var. Analoga, Phillips. PI. XXVIII, 



figs. 1, 2. 



Anomites wiOMBOii'ALis, Wahlenberg. Acta. Soc. Ups., vol. iii, p. 65, No. 7, 1821. 

 Puoducta depuessa, Sowerby. Min. Conch., pi. cccclix, fig. 3, 1823. 

 rugosa, Hisinger. Vetensk. Acad. Hand, for iir. 1826. 



1 It must be obvious to all, that the present work, whose publication will unavoidably have extended 

 over a number of years, can be fairly viewed but as a continual attempt to work out a great difficulty. 

 Availing myself, as I have constantly done, of every new discovery made by myself or by other competent 

 observers, and imbued with no preconceived idea, I have continually modified my views as science has 

 progressed ; and this I must plead as a valid excuse for the changes (contradictory, perhaps) which may be 

 noticed here and there in the many pages of which the monograph is composed. It is, however, my inten- 

 tion (should I ever be able to complete my arduous undertaking) to correct and co-ordinate the whole in the 

 concluding pages. 



