KO. 1342. 



SmOPSJS OF THE ASTARTIDAT-DALL. 



937 



Formula ^^^^^ {herouvalens<^ or ^^^^ (p<^mtidnm). Type, 

 GoodalUa herouvalemis Deshayes. p]ocenc of Paris. 



In considering- the distribution of the species the following- fihle 

 may aid in grasping.- its chief features. The East America.r fa'un'i 

 here is that south of Greenland, the West American that south of 

 Bering Strait. The Arctic fauna includes those north of those limits 

 an asterisk denoting that the species is conHned to tiie limits of its 

 fauna as above defined. 



ARCTIC AMERICAN FAUNA. 



A. undala. 



A. SiihicqnlJitlcrii. 



A. crenata. 



A. polaris. 



T. arctlca. 



T. borealis. 



T. fabuJa. 



T. hennettii. 



T. rernicosa. 

 T. eUiptica. 

 T. acntimstata* 

 T. globosa* 

 T. pulchella* 

 T. banksli.* 

 T. striata. 

 T. soror. 



WE.ST AMERICAN. EAST AMERICAN. 



A. polar in. ■\ 

 T. roUandi.* 

 T. arctica. f 

 T. borealis.-f 

 T. alaskensis.* 

 T. mmpacta.* 

 T.fabiila.t 

 T. bennpttii.-f 

 T. rt'rvicosa.'l 

 R. enquitnalti .* 



A. subiequilatera.-ff 

 A. castanea.* 

 A. undata. 

 A. crenafa.f 

 A. amithii.* 

 A. globula.* 

 A. nana.* 

 A. liogona.* 

 T. bore<dl.'i.'\' 

 T. t'llipfica.'\ 

 T. (jKddrans.* 

 T. striata.^ 

 T. soror. ^^ 



ANTARCTIC FAUNA. 



Axtartr I ongi rostra. 



From this it will be observed that the t^-pical Astartes, which are 

 rather abundant on the shores of Europe, compared with the Tri- 

 dontas, are in the majority on the Eastern coast, but in the Arctic they 

 form a much smaller proportion, and only one reaches the West 

 American fauna. Rictoci/ma is confined to the latter. In this hemi- 

 sphere the Arctic fauna has 4 peculiar species, Eastern America <>, 

 and Western America only -i. Only one species, .1. {Tridonfd) 

 ho real is^ is common to all three of the northern faunas. If we elim- 

 inate from the east and west faunas those really arctic species which 

 invade them from the north (and which are marked with a dagger in 

 the table), we find only the peculiar species left, except in the casi^ of .1. 



