Loop-hearing JBrachiopoda. 381 



so that the series of metamorphoses in each is quite distinct nearly 

 to the end. This in itself might not require that the austral and 

 boreal species should be referred to different genera and placed in 

 different subfamilies ; but when it is found that all the other 

 southern genera of the Terebratellidse represent arrested and 

 degraded stages in the development of a southern Terehratella or 

 Magellania, and that the northern genera represent similar stages 

 in the development of a northern high type, such a separation neces- 

 sarily follows. ^Moreover, these stages have a more profound signif- 

 icance, as several of them in both regions represent established 

 genera now extinct. 



A feature which ];nay be of service in distinguishing adult recent 

 shells is, that the Dallininae have small cardinal processes, and the 

 interior of the dorsal beak is usually grooved to the apex, while in 

 Magellaniinge, there is a well-developed projecting cardinal process 

 often filling the cavity of the beak. The lower genera can readily 

 be determined by the characters of the loop and by the median 

 septum which is generally low in the Dallininae and projecting above 

 the loop in the Magellaniinae. With these considerations in mind, 

 the metamorphoses and relations of the northern Terebratellidse may 

 be described. 



There are two finished types of northern genera, which are taken 

 as characteristic examples. One is the Macandrevia cranium 

 Miiller, and the other has been called Magellania ( Waldhehnia) 

 septigera Loven. In the light of the geographic, genetic, and onto- 

 genetic facts, the application of the law of morphogenesis necessi- 

 tates a new generic name for the second. Magellania, cannot be 

 retained, as the type is M. venosa from Terra del Fuego, and there- 

 fore belongs to the southern line having a different series of meta- 

 morphoses. Neither can it be referred to Macandrevia, on account 

 of its well-developed septum at maturity, nor to Endesia (type JE. 



* Platidia seems to be an exception in the distribution of the northern genera, as 

 it has been recorded from Marion Island, in the southern Indian Ocean. The northern 

 forms referred to Magasella are without the characteristic high septum of M. Cumingi 

 and appear to be stages of development of a higher northern form. 



In Fischer's " Manuel de Conchjdiologie," p. 1246, (Ehlert in discussing the geo- 

 graphical distribution of Brachiopods says : " Parmi les Brachiopods il en est dont la 

 distribution est en rapport avec la temperature regionale ; c'est ainsi qu'un certain 

 nombre d'. especes sont particulieres aux mers qui avoisinent les poles, chaque hemis- 

 phere ayant ses formes speciales qui lui appartiennent en propre, k I'exception de 

 Terebratulina caput-serpeniis, var. septentrionalis, qui se trouve a la fois dans I'hemis- 

 phere austral et dans I'hemisphere boreal." 



Trans. Conn. Acad., Vol. IX. March, 1893. 



27 



