November 10, 1905.] 



SCIENCE. 



601 



be settled by the process of elimination unless 

 we agree beforehand as to whether Flesus is 

 a valid genus, or as to what were the unex- 

 pressed purposes of Rafinesque. 



But common usage and common sense 

 agree in placing platessa, the common Plaice, 

 as the type of Pleuronectes. 



David Staer Jordan. 



an interesting cretaceous chimieroid 



EGG-CASE. 



Almost nothing is known of the structural 

 characteristics of the holocephalous fishes of 

 the Mesozoic period except dental plates or 

 teeth. The remains of such, however, are 

 numerous and about a score of generic names 

 have been proposed for them, although A. 

 Smith Woodward only fully recognizes five, 

 Ganodus, Iscliyodus, Edaphadon, Callorhyn- 

 chus and Elasmodectes. I was, therefore, 

 much interested in a fossil which Drs. Frank 

 H. Knowlton and T. W. Stanton referred to 

 me for identification, if possible, and which 

 I at once recognized as a chimseroid ovi- 

 • capsule apparently most nearly resembling that 

 of modern deep-sea forms. 



The interest arises frora the assumption 

 that where likeness prevail^ between such 

 products, not only the parts which frame them 

 but other structures must correspond. The 

 inference is not irrefragable, but in the ab- 

 sence of contradictory data, perfectly legiti- 

 mate as a provisional hypothesis at least. 



The fossilized egg-cases previously known 

 are few and the indications as to afiinities 

 interesting as well as important. Three 

 figures have been published of Jurassic egg- 

 cases, two by Emil Bessels and one by Otto 

 Jaekel. All are of the Callorhynchus type 

 and it is significant that a ' right palatine 

 tooth,' obtained from the ' Lower Greensand ' 

 of New Zealand, has been attributed by E. T. 

 Newton and Woodward to that genus and 

 named Callorhynchus hectori. 



The newly found fossil was obtained by Mr. 

 N. H. Darton, of the U. S. Geological Survey, 

 from ' massive sandstone ' a few miles west of 

 Laramie, Wyoming. 



The contour and general form are well pre- 

 served but not the details. The resemblance 



to the bvicapsules of Harriotta and Bhino- 

 chimcera lies in the absence of differentiation 

 between the anterior and posterior portions 

 of the lateral alse of the capsule and the 

 imiformity of the transverse costal ridges all 

 through. It differs from the ovicapsules of 

 both Harriotta and Bhinochimcera by the 

 greater width of the alse and especially the 

 greater width and extension forward along the 

 sides of the arehidome.^ The resemblance is 

 greatest to Rhinochimasra. 



The genus Harriotta was set apart as the 

 type of a subfamily (Harriottinse) by Gill, in 

 1896, and it was associated with Rhinochimcera 

 in a family (Ehinochimgeridse) by Garman, 

 in 1904. It is to this group (if a family,- 

 properly nameable Harriottidse) that the 

 Wyoming fossil belongs. It can not be corre- 

 lated with any one of the many generic names 

 {Eumylodus, Mylognathus, Dipristis, Sphage- 

 poea, Diphrissa, Bryactinus, Isotcenia and 

 Leptomylus) that have been especially coined 

 for American Cretaceous fossils, but the 

 naming of it, if such must be done, I leave 

 to Dr. Dean who is now publishing (through 

 the Carnegie Institution) an elaborate work 

 on the chimscroids. I have had the privilege 

 of looking over the proof-sheets of that work 

 and my knowledge of the ovicapsules of the 

 Ilarriottidse is chiefly derived from it, though 

 I had long ago seen those of Harriotta. 



If these determinations prove correct and 

 the groups named families by Garman are 

 accepted as such the curious deduction fol- 

 lows that no fossil ovicapsule of a typical 

 chimserid has been found as yet. 



Although the living harriottids are deep- 

 sea forms, it does not follow that a deep sea 

 is indicated for the habitat of the extinct 

 harriottid. The character of the sandstone 

 as well as of the basin in which the ovicapsule 

 was found is opposed to the hypothesis of a 

 deep sea. It must be remembered, too, that 

 the same genus may have species ranging 

 from shallow water to abyssal depths; Chim- 

 cera, for example, has a species (C. colliei) 

 which may be caught from a city wharf and 



^In the interest of conciiBeness of description 

 I would iise archidome for the chamber for the 

 head and -trunk of the chimseroid and urodome 

 for that receiving the caudal portion. 



