PALEOZOOLOGIE ET PALEOPHYTOLOGIE 



93 



The lower jaw consists of a dentary, arLiculare, prearticulare, angulares 

 surangulare. 



The hyoid inchide a hypohyal of a ceratohyal élément and there are four 

 ossified branchial arches. 



The ishoulder gkdle of one side is présent and associated with it the 

 humérus, radius, ulna of two metacarpals of a fore limbwhich was very 

 small ; from the head of the humérus to the extremity of the metacarpals 

 its measures less than one-half the leng the of the skull. The présence of 

 hind limbs has been announced by Miss Finney. 



The large and characteristic parasphenoid, the distinct roofmg bones, 

 large. prefrontal, the présence of a quadrate, but no jugal nor quadrato-jugal 

 are characters of the Urodeles ; more primitive are the well ossified basi- 

 occipital and supra occipital, the présence of a foramen for the twelfth nerve, 

 the nature of the condylar articulation of the skull, the présence of a separate 

 spisthotic large tabulares, conspicuous supratemporal bones, a complex 

 lower jaw and large well ossified branchial arches. 



Characters which appear to be pecuHar are the mode of union of the maxilla 

 with the palatine and of this bone with the vomer and pterygoid, the nature 

 of the vertebra and the curved form of the longribs. 



Author's abstrad. 



Sollas, W. J., The Skull of Icthyosaurus, studied in serial sections. 

 Phil. Trans. Roy. Soc. London, ser. B, vol. 208, pp. 63-126, 1 pi. Londres, 

 1916. 



A skull of /. communis, var. 520 mm. long, was treated so as to obtain a 

 séries of 520 serial sections and from thèse a reconstruction was built up in 

 plaister of Paris. A study of this material has not only placed our knowledge 

 of the cranial anatomy of Icthyosaurus on an exact basis but has yeilded 

 much fresh information. The relation of the basi-occipital to the basi-sphenoid 

 is described. The columella cranii are large plate-hks bones which extend 

 from the pterygoids to the pariétal bones with which they articulate. In front 

 of them is a pair of small bones, serially homologôus, which are distinguished 

 as the anterior columella. In the posterior région of the orbits the pariétal 

 bones are split into two wings in a manner recalhng the double roof the 

 Chelonia. Small septomaxillary bones are présent. A remarkable complex 

 union of the pariétal, frontal, post frontal, prefrontal, and nasal bones occurs 

 in front of the supratemporal fossa. The supposed coronoid of the lower 

 jaw is shown to be the goniale or prearticulare. There appears to be évidence 

 for the existence of small ossified branchial arches behind the hyoid. 



The Icthyosaurs présent many primitive characters which suggest a not 

 very remote Gotylosaurian ancestry. 



Author's ahslracl. 



Sclirœder, H., EociENE SiEUGETiERRESTE Aus Nord- und Mitteldeutsch- 

 LAND. Jahrb. kœn. pr. Geol. Lanclesanst., Bd. XXXVII, pp. 163-195, 

 pi, XXI-XXII. Berlin, 1916. 



