ON THE STRUCTURE OF THE LABYRINTHODONTS. 235 



One horse-power is about three quarters of an erg-ten per second. More 

 nearly, it is 7"46 erg-nines per second ; and one force-de-cheval is 7*36 erg-nines 

 per second. 



The mechanical equivalent of one gramme-degree (Centigrade) of heat is 

 41-6 megalergs, or 41,600,000 ergs. 



Appendix. 



Mr. Stoney has requested the insertion of the following extract from one 

 of his letters, written subsequently to the presentation of the foregoing 

 Report : — 



" Would you oblige me very much by putting on record, either in the 

 Report or as a footnote to it, that the centimetre was recommended as the 

 unit of length against my earnest remonstrance, and that I am in no degree 

 responsible for this decision. I would be glad to have the objections I urged 

 against it stated also. They were, ' that it is far too small, and that its mul- 

 tiples and submultiples cannot bo briefly designated. From its being too 

 small, it, in conjunction with the gramme and second, lands us in quite 

 out-of-the-way mechanical units — the unit of force which results being but 

 Httle more than the pressure of a milligramme, and the unit of work being 

 but little more than the hundredthousandth part of a grammetre. This 

 I deem a very serious objection.' 



•' I sttU thinlc that these awkward consequences, and the footing which 

 the metre has already gained in science, will prove fatal to the recommenda- 

 tion of the Committee, and that experience will show that the metre must in 

 the end be accepted as the standard unit of length." 



Report of the Committee, consisting of Professor Phillips^ LL.D., 

 F.R.S., Professor Harkness, F.R.S., Henry Woodward, F.R.S., 

 James Thomson, John Brigg, and L. C. Miall, on the Labyrin- 

 thodonts of the Coal-measures. Draion up by L. C. Miall, Secretary 

 to the Committee. 



[Plates I., II., III.] 



The Committee have to report that some of their number have personally 

 examined all the more important examples of Labyrinthodonts in European 

 collections, including at least one example of every species recorded from the 

 British Isles. They desire to thank many private collectors and officers of 

 public museums for facilities afforded. 



The preparation of a memoir on the classification of the Carboniferous 

 species is in progress ; meanwhile the Committee offer a preliminarj- sketch 

 of the structure of the Labyrinthodonts. 



The Skull {general). — The general figure of the skull varies greatly in this 

 order. It is usually triangular, with a rounded anterior end, and a concave 

 posterior border, but may be oval, parabolic, pyriform, or hexagonal. In 

 one species of Archegosaurus (A. Dechen'i) it is greatly produced, so that the 

 length exceeds twice the breadth. Jtlore commonly the greatest breadth is 

 nearly equal to the length. In Braclvjops the greatest breadth is rather 

 more than the length. The upper and lower surfaces of the cranium are 

 usually crushed flat. Rarely, as in the single skuU of Zygosaurus and in 

 one example of Loxomma, is the original contour preserved. 



1873. Q 



