1899 ] FRESH FACTS 215 



Sexual Dimorphism in Jurassic Nautili. G. C. Crick. " Description 

 of new or imperfectly known species of Nautilus from the Inferior Oolite, pre- 

 served in the British Museum (Natural History)," Proc. Malacol. Soc. iii. pp. 

 117-139, Dec. 1898. The observations of Willey on sexual dimorphism in the 

 recent Nautilus have satisfactorily dispelled any doubts as to the existence 

 of such a character, and divergences between individuals of any fossil species 

 may therefore be interpreted as due to sex. Of the eleven species here de- 

 scribed, seven appear to present both a broader form (male) and a narrower 

 form (female) occurring at the same locality and horizon. In some specimens 

 also it has been possible to trace very clearly the position of the anterior 

 boundary of the muscular attachment. A specimen of JY. bradfordensis shows 

 the black layer as a band enveloping the whorl immediately in front of the 

 aperture. A few non-adult specimens are described ; and it is interesting to 

 note that the British Museum specialist definitely accepts the approximation of 

 the last two septa as a criterion of maturity. 



A False Fossil. J. S. Diller. " Origin of Palaetrochis," Amer, Joum. 

 Science, vii. 1899, pp. 337-342. In 1856 Professor Ebenezer Emmons described 

 two species of Paleotrochis from the so-called Taconie rocks of Montgomery 

 County, in North Carolina, and regarded them as siliceous corals, and as the 

 oldest representatives of animal life upon the globe. But Hall, Marsh, J. A. 

 Holmes, and others denied their organic nature, whilst C. H. White almost as 

 strongly advocated it. Mr. Diller determines the Palaetrochis rock as an acid 

 volcanic full of spherulites, and concludes " that Paleotrochis, where most 

 perfectly developed and composed of granular quartz, is the result of deposition 

 after the spherulitic growths about it and within it had developed, but whether 

 this deposition followed soon after that of the spherulites in the course of solidi- 

 fication, or took place in hollow spherulites (lithophysae), or resulted perhaps 

 long subsequently at the time of rock alterations, is not so clear." But this 

 seems clear that the Paleotrochis is no reputable coral. 



Diplospondyly. W. G. Eidewood. " Some observations on the caudal 

 diplospondyly of sharks," Joum. Linn. Soc. (Zool.) xxvii. 1899, pp. 46-59. 

 It is a well-known fact that in Selachian fishes the vertebrae of the tail are twice 

 as numerous as the caudal segments as marked by the spinal nerves and the 

 intermuscular septa. Dr. Bidewood reviews the facts and comes to the conclu- 

 sion, " that the condition of diplospondyly in the tail of sharks is secondary, but 

 of ancient date ; and, further, that it is purely adaptive, being calculated to 

 maintain a due proportion between length of centrum and width of body, with- 

 out diminishing the length of the muscle-segments. In the region of the body 

 from the cloaca to the caudal fin, the demand for increased flexibility is pre- 

 potent over the normal tendency of the chondrified chordal sheath to segment 

 in such a way that the centra are as numerous as the myotomes." 



Teratologia. Bertram C. A. Windle. " Ninth report on recent terato- 

 logical literature," Joum. Anat. Physiol, xxxi. pp. 507-526. In this valuable 

 record, for the continuation of which all biologists should be grateful, Prof. 

 Windle gives a clear and terse summary of recent progress. He gives references 

 to 83 papers, and arranges the results under the headings : — experimental, 

 general, duplicity, head and neck, thorax, abdomen, genitalia, and extremities. 



