Febbuaby 11, 1910] 



SCIENCE 



233 



the scale can be adjusted with ease and pre- 

 cision by moving the tripod on its shelf. With 

 the lens used in my apparatus, which is 8 cm. 

 in diameter, the range of the latter adjustment 

 is very great. 



The galvanometer mirror used here is f 

 inch in diameter. The lamp can be operated 

 with either direct or alternating current, and 

 the image is so bright that it has never been 

 necessary to darken the room. The inexpen- 

 sive lamp of the type used here is provided 

 with a metallic hood, and with a pin hole and 

 mica screen for adjusting the arc, which is 

 controlled by hand. As used in this arrange- 

 ment the edge of the hood is horizontal. 

 While the round image of the carbon tip is 

 sharp enough for all ordinary purposes, read- 

 ings being taken to tenths of scale divisions, 

 yet if it is desired to make one edge of the 

 image straight and perfectly steady, this can 

 be done simply by laying a bar of metal on the 

 hood and moving it partly over the carbon 

 until the adjustment is correct. By using a 

 larger mirror on the galvanometer a more 

 brilliant image could of course be obtained. 



The arrangement described above has been 

 in use here for over a year. During the pre- 

 ceding three years an automatic lamp with 

 vertical carbons and an extra mirror were 

 used instead of the hand regulated 90° lamp. 

 The second arrangement has proved to be 

 more satisfactory than the first. An auto- 

 matic 90° lamp would of course be still more 

 satisfactory. 



S. J. Barnett 



The Tulane Univebsity of Louisiana 



THE amphibia of THE MAZON CREEK SHALES 



There have been but two species of Am- 

 phibia recognized from the shales which are 

 exposed along Mazon Creek, Illinois. These 

 two species are the remarkable reptile-like 

 microsaurian AmpMhamus grandiceps de- 

 scribed in 1865 by Professor Cope and the 

 salamander-like branchiosaurian described the 

 past year by the writer under the name Mi- 

 crerpeton caudatum. It is thus with consid- 

 erable interest that the writer is able to an- 

 nounce the discovery of seven additional species 



distributed in six additional genera. This 

 new and considerable addition to the knowl- 

 edge of the Mazon Creek fauna is made pos- 

 sible through the courtesy of Drs. Schuchert 

 and Eaton, of Tale University, who very 

 kindly placed at the writer's disposal the 

 entire collection of Mazon Creek Amphibia 

 belonging to that institution. 



The material is represented by ten speci- 

 mens, including the most perfect example of 

 AmpMhamus grandiceps so far seen. This 

 specimen makes possible the verification of the 

 author's restoration of that form and the addi- 

 tion of the ischia. The other specimens are 

 undescribed and represent a diverse fauna. 

 An additional species of the family Amphib- 

 amidffi is represented by a well-preserved an- 

 terior half of a skeleton. Three additional 

 branchiosaurian species are preserved. One 

 of these species, represented by two specimens, 

 is most remarkable for the preservation of the 

 entire alimentary canal and a portion of the 

 oviducts in both specimens. This on com- 

 parison with living Amphibia proves to show 

 close resemblances to the alimentary canal of 

 an immature branchiate individual of Die- 

 myctylus torosus Eschscholtz from a fresh- 

 water pond on Orcas Island in Puget Sound. 

 The other two species are remarkably like 

 Branchiosaurus of Saxony, but difl^er in hav- 

 ing an extremely elongate tail. 



Perhaps the most interesting discovery in 

 this new material is that of a primitive em- 

 bolomerous amphibian of the order Temno- 

 spondylia. It is related to Cricotus and may 

 be placed in the family Crieotidaa. It differs 

 from Cricotus, however, in the form of the 

 centrum and the relatively greater length of 

 the component elements. The notochordal 

 canal is widely open. A sixth species is 

 founded on a fore limb which shows relation- 

 ships to the family Molgophidas, which has, 

 so far, been known only from the Coal Meas- 

 ures of Linton, Ohio. 



Our knowledge of the amphibian fauna of 

 the Pennsylvanian up to the present time 

 would indicate that the forms had already 

 developed into local groups which had few 

 connecting types. We may regard the new 



