1:^6 MR. A. S. WOODWARD ON [Feb. 21, 



tainly not lessened by current advance, for Boas has lately shown 

 most conclusively^ that the pulmonary artery is homologous through- 

 out the vertebrate series. 



2. Palaeontological Contributions to Selachian Morphology. 

 By A. Smith Woodward, P.G.S., F.Z.S., of the British 

 Museum (Natural History). 



[Eeceived January 17, 1888.] 



I. On the Lateral Line of a Cretaceous Species q/Scylliidse. 



It has long been known that the canal investing the sense-organs 

 of the "lateral line" in Selachian fishes attains, as a rule, to a 

 considerably higher stage of development than in the Chinia^roids. 

 While in the latter the canal is merely an open groove, supported 

 by a series of incomplete ling-like dermal calcifications, in the 

 former it assumes a tubular character, opening externally by a row 

 of small orifices, either in its own roof, or through short secondarily 

 developed diverticula. 



Only two undoubted exceptions to this rule appear to have hitherto 

 been placed on record. The \ivm^ Echinorhinus is shown by Sol'.er^ 

 to have the lateral line in the form of an open groove, though this 

 apparently is not supported by any minute calcifications ; and very 

 similar is the lateral line of Chlamydoselachus, as described by Gar- 

 man^. The supposed Liassic Selachian, Squalor aja, may also be 

 assumed to have exhibited a similar condition of this organ, the small 

 half-rings originally supporting it being very clearly seen in several 

 fossils recently described before this Society ^, and agreeing in every 

 respect with those met with in Ischyodus and Chimcera. Both of the 

 first-named genera, however, are of a comparatively primitive cha- 

 racter, and Squaloraja shows several other marks of resemblance 

 to the Chimaeroids, so that the fact is not unexpected. But I have 

 lately observed suggestive traces of a similarly embryonic lateral line 

 iu a most specialized modern type of Selachian ; and as this appears 

 to be an unlooked-for novelty, it may be deemed worthy of a brief 

 note. 



The Shark in question is a small fossil species, discovered in the 

 Upper Cretaceous strata of Mount Lebanon, Syria, and provisionally 

 assigned by Pictet and Humbert" to the genus Sci/Uium, under the 



' "Ueb. d. Arterien bogen der Wirbelthiere," Morpholg. Jalirb. vol. xiii. 

 1887, p. 115. See also ibid. vol. vii. p. 488, and vol. viii. p. 169. 



^ B. Solger, ' Neue Untersuchungen ziir Anatomie der Seitenorgane der 

 Fisclie,' Arcbiv mikr. Anat. vol. xvii. (1880), p. 96. 



"^ S. Garman, " Chlamydoselachus anguineus, Garm., a living species of Clado- 

 dont Shark," Bull. Mus. Comp. Zool. Harvard Coll. vol. xii. no. 1 (1885), p. 3. 



* Smith Woodward, ' Note on the Lateral Line of Squaloraja' P. Z. S. 1887, 

 p. 481. 



' F. J. Pictet et A. Humbert, 'Nouv. Eech. Poiss. Foss. Mont Liban,' 

 p. Ill, pi. xviii. fjgs. 2-4. 



