3 so C. E, Beecher — Revision of the Families of 



austral types of terebratuloicls, exclusive of the genera of Terebra- 

 tulidffi, as here restricted, are Magasella {31. Cumingi), Kraussina, 

 Megerlina, and Bouchardia. In their brachial supports, these all 

 approximate early stages of the higher genera, Magellania and 

 Terebratella. They must be regarded as arrested and degraded 

 forms. 



The brachial supports in Kraussina and Bouchardia are merely 

 portions of the ascending branches, or secondary loop, on the sep- 

 tum, without any traces of the descending branches, or primary 

 lamellge. These genera may be compared with the houchardiforni 

 stage of Terebratella dorsata. One grade higher is exhibited in 

 Megerlina (type M. LamarcMana Dav.) in which there is added to 

 the Kraussina structure two processes apparently homologous with 

 the points belonging to the descending branches appearing on the 

 septum in the niegerliniform stage of T. dorsata. These atavistic* 

 genera are all austral in their distribution, but not strictly polar, 

 occurring as they do off the coasts of South Africa, Brazil, Aus- 

 tralia, St. Paul's Island, etc. 



In reviewing this group of genera, it is seen that the highest 

 member of the series is Magellania, which reaches its maximum 

 development in size and number of species in antartic seas. The 

 next genus belcw^, Terebratella, ranges still farther toward the equa- 

 tor, while the atavistic types Krausshia, Megerlina, and Bou- 

 chardia, do not occur in j^olar regions, but are nevertheless austral 

 in their distribution. 



Balliniiice. 



The northern hemisphere furnishes a series of genera and species, 

 which, passing through a different and distinct series of loop meta- 

 morphoses, attains in the higher members the same result as those 

 of the southern fauna, constituting a case of exact parallel develop- 

 ment. Thus the northern Macandrevia cranium, Ballina septigera, 

 D. Baphaelis, D. Grayi, Terebratalia transversa, T. coreanica, 

 T. spitzbergensis, and T. frontalis, are very similar in the adult 

 characters of the loop to the southern Magellania venosa, M. ker- 

 guelenensis, M. Wyvillii, M. flavescens, M. lenticxdaris, Terebratella 

 dorsata, T. cruenta, and T. rubicunda. It is only when their devel- 

 opment is examined that a difference is manifest. 



By observing the stages of development in the austral and boreal 

 terebratellids, it is seen that both start from a common larval stage, 

 and divergence into two lines begins in the first adolescent stages. 



