722 



SCIENCE. 



[N. S. Vol. V. Ko. 123. 



and reaches the following result : The re- 

 puted humerus is the interclavicle ; the re- 

 puted scapula is the humerus ; the reputed 

 supra-scapula is the left coracoid; the re- 

 puted supra-scapula is the right scapula ; 

 the reputed right and left coracoids are the 

 pre-coracoid (epicoracoid) and coracoid of 

 the right side ; the reputed clavicles are 

 ribs. Five digits are identified in place of 

 four. The fossil is referred to a new genus 

 — Aristodesinus. It is identified as an Ano- 

 modont reptile, chiefly on the basis of re- 

 semblence to Procoloplion and Pareiasaurus. 

 He also compares it with the Monotremata. 

 In conclusion, he argues that the points 

 of structure are so few in which Mono- 

 treme mammals make a closer approxi- 

 mation to the higher mammals than is 

 seen in his fossil (Aristodesmus) and other 

 Anomodontia, that the Monotreme resem- 

 blances to fossil reptiles become increased 

 in importance. He believes that a group 

 TJieropsida might be made to include Mono- 

 tremata and Anomodontia, the principal diff- 

 erences (other than those of the skull) 

 being that Monotremes preserve the marsupial 

 bones, the atlas vertebra and certain cranial 

 sutures. Aristodesmus, which suggests this 

 link, is at present placed in the Procolophonia, 

 a group separated from its recent associ- 

 ation with Pareiasaurus, and restored to its 

 original independence because it has two 

 occipital condyles [ ! ] , with the occipital 

 plate vertical, and without lateral vacuities, 

 and has the shoulder-girdle distinct from 

 Pareiasauria in the separate precoracoid 

 extending in advance of the scapula. In 

 the same remarkable communication Seeley 

 discusses, also, the relation of the Laby- 

 rinthodont type to the existing Amphibia, 

 and regards the Labyrinthodont osteology as 

 demonstrating closer relationship with Ichthyo- 

 sauria and Anomodontia. The group is there- 

 fore regarded as reptilian, forming a branchiate 

 division of the class [ / ] . What are such wild 

 speculations good for ? 



To conclude I give the synonyms of this 

 reptile.* 



Sclerosaurus armatus, H. v. Meyer. Neues 

 Jahrbuch f. Min., 1867, p. 136. 



Labyrinthodon Rutimeyeri, Wiedersheim, 

 Abhandl., Schweiz. Pal. Gesellsch. v. 1878, 

 p. 1-56. 



Aristodesmus Rutimeyeri (Wiedersheim) ; 

 Seeley, Ann. Mag. Nat. Hist. (6), Vol. 17, 

 1896, p. 183. 



G. Baue. 



The Univeesity of Chicago. 



CURRENT NOTES ON PHYSIOGRAPHY. 

 MCGBB ON SHEETFLOOD EROSION. 



Sheetflood is a term coined by McGee 

 (Bull. Geol. Soc. Amer., VIII., 1897, 87- 

 112) to name the thin sheets of water that 

 occasionally flow over the thinly gravel- 

 covered intermont slopes of the Sonoran 

 district in Arizona and bordering Mexico. 

 It is contrasted with streams, in which a 

 water ciirrent is gathered into a channel. 

 Sheetfloods may be a mile or even ten miles 

 wide, yet only a foot or two deep, running 

 rapidly down slopes of one or two hundred 

 feet to a mile; everywhere 'at grade;' that 

 is, their ability to do work everywhere 

 nicely balanced against the work that they 

 have to do. By sheetfloods, not by streams, 

 the peculiar gravel-covered rock floors of 

 the Sonoran district are thought to have 

 been planed down ; and the abrupt transi- 

 tion from streams in the mountain gullies to 

 sheetflood on the piedmont surface is taken 

 to explain the equally abrupt transition 

 from mountain to plain ; the rocks remain- 

 ing the same. Unlike the aggraded plains 

 of the Utah, where intermont depressions 

 are heavily filled with mountain waste, the 



* Basileosaurus Freyi Wiedersheim (TJber einen 

 neuen Saurus aus der Trias. Mit einer Tafel. Abh. 

 Schweiz. Pal. Ges., vi., 1879, 4 pp.) from Eiehen is 

 too insufficiently described and figured to determine 

 its true position. It is doubtless a reptile, but, ac- 

 cording to Wiedersheim, not Sclerosaurus. 



