68 



NA TURE 



[Nov. 20, i< 



yielded by the observations I have made, when grouped together 

 roughly according to altitude. The results are : — 



Approximate 

 No. of Mean upper Mean lower Mean upper Mean lower value of 

 obs. height height velocity velocity exponent in 



formula 



6 ... 249 ... 93 ... 1630 ... 1 145 ... J 

 S ... 412 ... 173 ... 1751 ... 1474 ... I 

 4 ... 634 ... 324 ... 1987 ... 1902 ... iV 

 Thus, while the velocity invariably increases as we ascend, the 

 rate rapidly diminishes after the first 200 or 300 feet. It must, 

 however, be remembered that the place of observation is itself 

 500 feet above sea-level, and though this would probably not 

 affect the results near the surface, the air above 200 feet must be 

 moving with very nearly the same velocity as it would have at 

 its real elevation above a sea-level Mirface. Adding therefore 

 the 500 feet to both heights in the case of the two last groups, we 

 get, for the value of x, J and \ instead of \ and T V These two 

 values are probably nearer the truth than those in the table, and 

 hover round the mean value \, which I have already stated was 

 found to hold for Vettin's cloud velocities up to 25,000 feet. In 

 any case it is plain that Mr. Stevenson's formula cannot be taken 

 to hold beyond his 50-foot pole. 



Further observations will, I trust, give a trustworthy basis for 

 determining the variations in the velocity-increment correspond- 

 ing to the direction and absolute velocity of the wind as well as 

 those corresponding to season, humidity, temperature, and pres- 

 sure. To thoroughly investigate the velocity-increment under 

 all such conditions, and thus to afford data to the physicist who 

 desires to construct the hitherto unwritten science of aero- 

 dynamics, will be one of the objects of my experiments during 

 the coming year. 



P. S. October 22. — Since the foregoing observations were 

 made I have succeeded in getting readings with the anemometers 

 at heights of over 1 100 feet above the ground, or 1600 feet above 

 sea-level. 



THE CLASSIFICATION AND AFFINITIES OF 

 DINOSA UKIA N REP TILES l 



T N this paper the author presented briefly the results of a study 

 ■*■ of Dinosauiian reptiles on which he had been engaged for 

 several years. The complete results will be published in a series 

 of monographs now in preparation. The material on which 

 the investigation is mainly based consists of the remains of 

 several hundred individuals of this grotip collected in the Rocky 

 Mountains by the author, and now preserved in the museum of 

 Yale College. Other important American specimens have been 

 examined by the author, who has also studied with care the 

 more important specimens of this group in the museums of 

 Europe. The investigation is not yet completed, but the results 

 already attained seem to be of sufficient interest to present to 

 the Association at this time. 



In previous publications on this subject the author had ex- 

 pressed the opinion that the Dinosauria should be regarded, 

 not as an order, but as a sub-class, and his later researches con- 

 firm this view. The great number of subordinate divisions in 

 the group, and the remarkable diversity among those already 

 discovered, indicate that many new forms will yet be found. 

 Among those already known there is a much greater difference 

 in size and structure than in any other sub-class of vertebrates, 

 with the exception of the placental mammals. Compared with 

 the Marsupials, living and extinct, the Dinosauria show an 

 equal diversity of structure and size. 



According to present evidence, the Dinosaurs were confined 

 entirely to the Mesozoic Age. They were abundant in the 

 Jurassic, and continued in diminishing numbers to the end of 

 the Cretaceous period, when they became extinct. The great 

 variety of forms that flourished in the Triassic renders it more 

 than probible that some members of the group existed in the 

 Permian period, and their remains may be brought to light at 

 any time. The Triassic Dinosaurs, although very numerous, 

 are known to-day mainly from footprints and fragmentary osseous 

 remains ; hence, many of the forms described cannot at present 

 be referred to their appropriate divisions in the group. From 

 the Jurassic, however, during which period Dinosaurian reptiles 

 reached their zenith in size and numbers, representatives of no 

 less than four well-marked orders are now so well known that 



al Meeting 1 f the British Association, by Prof. 



different families and genera can be very accurately determined, 

 and almost the entire osseous structure of typical examples, at 

 least, can be made out with certainty. Comparatively little is 

 yet known of Cretaceous Dinosaurs, although many have been 

 described from incomplete specimens. All these appear to 

 have been of large size, but much inferior in this respect to 

 the gigantic forms of the previous period. The remains best 

 preserved show that, before extinction, some members of the 

 group became quite highly specialised. 



Regarding the Dinosaurs as a sub-class of the Reptilia, the 

 forms best known at present may be classified as follows : — 



Sub-Class DINOSAURIA. — Premaxillary bones separate; 

 upper and lower temporal arches ; rami of lower jaw united in 

 front by cartilage only ; no teeth on palate. Neural arches of 

 vertebra? united to centra by suture ; sacral vertebra; co-ossified. 

 Cervical and thoracic ribs double-headed. Ilium prolonged in 

 front of acetabulum ; acetabulum.formed in part by pubis ; ischia 

 meet distally on median line. Fore and hind limbs present, the 

 latter ambulatory and larger than thosejn front ; head of femur 

 at right angles to condyles ; tibia with procnemial crest ; fibula 

 complete. First row of tarsals composed of astragalus and cal- 

 caneum only, which together form the upper portion of ankle 

 joint. 



(I.) Order Sauropoda (Lizard-foot). — Herbivorous. Pre- 

 maxillary bones with teeth. Large antorbital opening. Anterior 

 nares at apex of skull. Post-occipital bones. Anterior vertebrae 

 opisthoccelian ; cervical ribs co-ossified with vertebra; ; pre-sacral 

 vertebra; hollow ; each sacral vertebra supports its own trans- 

 verse process. Fore and hind limbs nearly equal ; limb bones 

 solid. Feet plantigrade, ungulate ; five digits in manus and 

 pes; second row of carpal and tarsal bones unossified. Sternal 

 bones parial. Pubes projecting in front, and united distally by 

 cartilage!; no post-pubis. 



(1) Family Atlantosaurida. — A pituitary canal. Ischia directed 

 downward, with expanded extremities meeting on median line. 

 Sacrum hollow. Anterior caudals with lateral cavities. Genera : 

 Atlantosaurus, Apalosaurus, Brontosaurus. 



(2) Family Diplodocidce. — Dentition weak. Brain inclined 

 backward. Large pituitary fossa. Two antorbital openings. 

 Ischia with straight shaft, not expanded distally, directed down- 

 ward and backward, with ends meeting on median line. Caudals 

 deeply excavated below. Chevrons with both anterior and 

 posterior branches. Genus : Diplodocus. 



(3) Family Morosauride. — Small pituitary fossa. Ischia 

 slender, with twisted shaft, directed backward, and sides 

 meeting on median line. Anterior caudals solid. Sacral 

 vertebra; solid. Genus : Morosaurus. European forms of this 

 order : Bothriospondylus, Ceteosaurus, Eucamerotus, Orni- 

 thopsis, Pelorosaurus. 



(II.) Order Stegosauria (Plated Lizard). — Herbivorous. 

 Feet plantigrade, ungulate ; five digits in manus and pes ; second 

 row of carpals unossified. Pubes projecting free in front ; post- 

 pubis present. Fore limbs small ; locomotion mainly on hind 

 limbs. Cervical ribs free. Vertebrae and limb bones solid. 

 Osseous dermal armour. 



(I) Family Slcgosauridcc. — Vertebrae bi-concave. Neural canal 

 in sacrum expanded into large chamber ; ischia directed back- 

 ward, with siites meeting on median line. Astragalus co-ossified 

 with tibia ; metapodials very short. Genera : Stegosaurus 

 (Hypsirhophus), Diracodon ; and in Europe, Omosaurus (Owen). 



2. Family Scelidosauridcz. — Astragalus not co-ossified with 

 tibia ; metatarsals elongated ; four functional digits in pes. 

 Known forms all European. Genera: Scelidosaurus, Acantho- 

 pholis, Crata;omus, Hyla'osaurus, Polacanthus. 



(III.) Order Ornithopoda (Bird-foot). — Herbivorous. 

 Feet digitigrade, five functional digits in manus and three in 

 pes. Pubes projecting free in front ; post-pubis present. 

 Vertebra; solid. Cervical ribs free. Fore limbs small ; limb 

 bones hollow. Premaxillaries edentulous in front. A pre- 

 mandibular bone. 



( 1 ) Family Camptonotida. — Clavicles wanting ; post-pubis com- 

 plete. Genera : Camptonotus, Laosaurus, Nanosaurus ; and in 

 Europe, Hypsilophodon. 



(2) Family Iguanodontidie. — Post-pubis incomplete. Pre- 

 maxillaries edentulous. Known forms all European. Genera : 

 Iguanodon, Vectisai 



