THE MICROSAURIAN FAMILY HYLONOMID.E. 79 



Credner (186), Fritsch (251, Bd. i, p. 89, Taf. 12, figs, i, 4, 15), and Woodward 

 (629) have referred remains of Microsauria discovered in the Coal Measures or 

 lower Permian deposits of Saxony, Bohemia, and Lancashire, England, to the genus 

 IIvloiioHius. There is much uncertainty as to the validity of these references, due 

 to the uncertain nature of the type of Hylono-mns. There are 4 American species 

 of the genus: Hyloiionins lutiilcns Dawson, II. I yell i Dawson, //. mult ideas Dawson, 

 and //. wymani Dawson. All the species are from the Coal Beds at the South 

 Joggins, Nova Scotia. 



Hylonomus lyelli Dawson. 



I )A\VSON, Quart. Jour. Geol. Soc. London, xvi, p. 274, figs. 14 to 18, 1860. 



DAWSON, Air-brcathcrs of the Coal Period, p. 44, 1863. 



DAWSON, Phil. Trans. Roy. Soc. London, 1882, pt. n, p. 635, pi. 39, figs. I to 14 and 27. 



DAWSON, Acadian Geology, 3d cd., 1880, p. 370. 



Type: Specimens Nos. R 443 to 445 in the British Museum (393, pt. IV, p. 223). 

 Horizon and locality: Coal formation of the South Joggins, Nova Scotia. 

 This species is by far the most abundant (plate 9) in the erect trees examined by 

 Dawson. Its characters Dawson (216) defines as follows: 



' ' General form lizard-like, with the hind limbs rather larger than the fore limbs. Length 

 when mature, 5 to 6 inches. 



"Head somewhat elongate; bones of skull smooth or with microscopic striae, perfectly 

 united, except at the parietal foramen. Occipital condyle double, and apparently bony. 

 Teeth simple, conical, numerous, about forty in each mandible, and nearly equal, except that 

 a few of the anterior ones are rather larger than the others. The teeth are anchylosed to 

 the jaw in a furrow protected by an external bony plate. 



' ' Vertebrae with cylindrical bodies, slightly concave at the ends. When partly exfoliated 

 they appear hour-glass-shaped, in consequence of the internal cartilage having the form of 

 two cones attached by their apices. Zygapophyses conspicuous above; neural arches united 

 to the bodies of the vertebrae, and with broad neural spines. Dorsal vertebrae with strong 

 lateral processes. Caudal vertebrae apparently simple and cylindrical. Number of verte- 

 brae in neck and trunk about thirty. 



"Ribs long and curved, with capitulum and tuberculum, cartilaginous within. 



"Anterior limb slender, humerus with distinct keel; radius and ulna separate; toes four 

 or five. 



"Posterior limb with well-developed femur; tibia and fibula shorter, separate; toes 

 five, somewhat long and slender. 



"Pelvis large, composed of ilium and ischium." 



Interclavicle and numerous scutellae are present. Upper surface protected with 

 imbricated horny scales. In front two rows of horny tubercles and plates, with 

 epaulettes composed of bristle-like fibers projecting from the skin. 



The animal possibly fed on insects, as is indicated by the coprolitic matter asso- 

 ciated with the remains of the species. 



The following measurements are given by Dawson for the largest individual 

 discovered : 



Length of head about cm. 2 Length of rib cm. 1.3 



Length of neck 1.3 Length of humerus " 1.4 



Length of trunk . 7 Length of femur " 1.8 



Length of posterior limb to heel cm. 3 Length of tibia " 1.2 



Length of mandible. . 1.8 Length of body of vertebra mm. 2.> 



Teeth, 5 in I mm. 



