SOME NEW DEVONIC FOSSILS 289 



and distant concentric lines which are mostly continuous though 

 somewhat undulated but these frequently inosculate and become 

 separated by narrower intervals toward the anterior margin. 

 Length 17 mm, greatest diameter 13 mm. 



This shell is like L. p e r 1 a t a Hall and L. spatiosa Hall 

 of the Helderbergian as the outline of those species has been rep- 

 resented but in this respect conjoined with the peculiar character 

 of its surface markings, I am unfamiliar with any other species, 

 like it. 



Lozver Devonic. Grande Greve, P. Q. 



BRYOZOANS 

 Hederella blainvillii sp. no v. 



This very interesting bryozoan incrusts the shells of L e p t o s - 

 trophia blainvillii Billings and, so far as our observation 

 has extended, seems to attach itself always to the ventral or upper 

 valve at an early stage in the life of the brachiopod and grow out- 



Hederella blainvillii 



ward from the parent cell in all directions, keeping the apertures, 

 of the cells at or just a little distance above the margins of the shell. 

 This habit evinces a true commensal condition not often shown in 

 other cases of attached bryozoa ; the water currents set up by the 

 ciliated mantle of the brachiopod have helped to feed the members 

 of the bryozoan colony, most of which stand in an attitude of readi- 

 ness for this service. This species occurs with extraordinary fre- 

 quency on these brachiopod shells and seems to grow on no other 

 save for an occasional simply branched stock on an upper valve of 

 Chonetes hudsonicus. Hederella ramea which I 

 have described from the Oriskany of Becraft mountain, N. Y. 

 elects attachment to Leptostrophia oriskania, always 

 keeping its apertures toward the opening of the shell valves. From 



