III. Croonian lecture.—Researches on the structure, organization, and classification of the fossil Reptilia.—II. On Pareiasaurus bombidens (Owen), and the significance of its affinities to Amphibians, Reptiles, and Mammals

The genusPareiasaurus was instituted by Sir Richard Owen in 1876 for a large number of Reptilian remains from the Karroo Series of strata of South Africa. It was classed with the Dinosauria in a new family named Serratidentia, and regarded as represented by two species, which were namedP. serridens andP. bombidens . Its place among the Dinosauria was held to be established by the teeth, which were compared to those ofIguanodon in their mode of implantation, and to those ofScelidosaurus in their close arrangement and nearly uniform wear, while the margins of the crown are similarly notched or serrate. The cranial characters are stated to concur with the dental characters in supporting the formation of a family in the Dinosaurian order for these fossils. Unfortunately the type-skull ofPareiasaurus serridens is now only known from a plaster cast, and by some small fragments cut from the lower jaw. The immense development of the so-called malar processes, which overlap the lower jaw and suggested the generic name, was regarded as showing a resemblance to the genusAnthodon from South Africa, and in a less degree toScelidosaurus from the Lias of Charmouth. Regarding the fossil as a vegetable feeder, Sir R. Owen remarked that the homologous descending malar process among Mammals is found only in those types which come nearest to Reptiles in brain structure, such as Kangaroos, Sloths, and Megatheroids. In the cervical vertebræ sub-vertebral wedge-bones are found, which are likened to those which are said to occur in the fore part of the neck of Ichthyosaurs and Plesiosaurs. A notochordal canal penetrates to the centre of the centrum without piercing it, sometimes in a way almost Ichthyosaurian, but sometimes as a slender conical tube extending from the flattened articular face of the centrum. Sir R. Owen remarks, it is a trace of a lower grade of vertebral structure, and 'recalls the more widely perforated, still less ossified, centrums of the vertebræ of Ganocephalous Reptiles of the Carboniferous Series represented byParabatrachus ,Hylonomus ,Dendrerpeton , &c.' The ribs are double-headed, with a parapophysial articulation on the centrum, a diapophysial facet on the neural arch. The scapula and coracoid are said to be anchylosed together. The humerus is described as relatively broader than inOmosaurus , rather suggesting the breadth of the bone in the Mole. The bone is solid. Other parts of the skeleton are identified; but no further suggestions are made as to the organic relations of the type.