1884.] Ol i [Cope. 



and that the posterior one cannot be said to be within the oral cavity, as 

 is the case in the known families of the Dipnoi. It is probable that there 

 is a frontoparietal foramen at the posterior bifurcation of the frontal bones, 

 corresponding to the conarium or pineal body of the brain. In a cranium 

 broken across just anterior to the bifurcation, a canal passing forwards 

 and downwards is exposed. There is a foramen, or possibly only a deep 

 fossa on each side of the middle line on the occipito-sphenoid suture. The 

 foramen magnum is rather small and opens upwards. Its border displays 

 no articular surfaces. At the middle of a line connecting the posterior 

 borders of the postorbital processes is a small shallow fossa, or probably 

 foramen, from this there extends on each side backwards and outwards, a 

 shallow groove apparently for a vessel, which terminates at the anterior 

 one of three foramina already mentioned as in line with the fissure which 

 distinguishes the lateral ala of the basicranial axis posteriorly. A similar 

 groove connects the first and second of these foramina, and in one speci- 

 men the groove from the median foramen joins this connecting groove. 

 In front of the median foramen is a rather larger one on the median line, 

 situated at tbe fundus of a short longitudinal groove. It is placed just 

 posterior to a line connecting the preorbital processes. The grooves easily 

 become obsolete by weathering. 



II. Affinities. 



In determining the systematic position of this animal, it will be con- 

 venient to take a survey of the characters of the primary divisions of the 

 fishes. In 1840 Bischoff published the first account of the osteology of 

 Lepidosiren. In this description he called the frontal bones malars with 

 a question, and the parietals frontoparietals. He described the skull as 

 having an os quadratum. In 1854, Stannius in the Handbuch der Zoo ■ 

 tomie* correctly determined the frontals and parietals, and stated further 

 that the "lower jaw and hyoid bone articulate directly with continuous 

 processes of the chondrocranium." This appears to be the first correct 

 description of the cranial structure of the Dipnoi. In 1864, f Huxley re- 

 stated the view of Stannius as to the nature of the mandibular articula- 

 tion ; adopted the opinion of Bischoff that the frontal is a frontoparietal, 

 and took a new position in calling the frontals supraorbitals. He also 

 restates in general, the description of the skull of the Holocephali already 

 given by Stannius. 



The system of Johannes Mtiller, adopted by Stannius, was a great im- 

 provement over preceding ones. It embraced, however, the error of in- 

 cluding the Holocephali in the same sub-class (Elasmobranchi) with the 

 sharks. This was adopted by Gill in 18614 by Huxley in 1864 § and in 

 1871. || All of these authors adopt at these dates the sub-class Ganoidea. 



*Erstes Buch, die Fische, p. 49. 



t Elements of Comparative Anatomy, p. 210. 



J Catalogue of the Fishes of the East Coast of North America, p. 24. 



§ Elements of Comparative Anatomy. 



J The Anatomy of Vertebrated Animals, p. 120. 



