Prof. Dr. T. G. Bonneij — Troldolite, etc., in Aberdeenshire. 439 



following remark (Bulletin of Museum of Comparative Zoology, 

 Cambridge, Mass., 1881, vol. ix. p. 78): "It seems to have been 

 overlooked until now, that we are indebted to Sowerby for its 

 characterization, and that he is entitled to be cited as authority for 

 the genus." But on referring to James de Carle Sowerby's descrip- 

 tion of the genus Pleurotomaria,^ Min. Conch, vol. vii. p. 69, pi. 640 

 (published November, 1844), he cites Defrance as his authority. 



It is true that in Defrance's " Tableau des CorjDS Organises Fossiles" 

 (8vo. Paris, 1824), he merely gives the name (p. 114) ; but in the 

 " Dictionnaire des Sciences Naturelles " (vol. xli. 1826, p. 381), De 

 Blainville adopts Defrance's name, and credits him with most of the 

 new species described. It is also perfectly true that Sowerby 

 defined, the genus, but to assume that he founded it would be unjust 

 to Defrance, especially since both De Blainville and Sowerby have 

 given Defrance credit for the genus. If such a rule, as is thus pro- 

 posed by Mr. W. H. Dall, were generally adopted by naturalists, 

 endless confusion would arise and great injustice would be done to 

 all the older naturalists whose work laid the foundation for the 

 researches of the generation of younger men who have followed after. 



EXPLANATION OF PLATE XI. 



Fig. 1«. Pleurotomaria Bei/richii, B.ilgendovi. Recent. Enoshima, Japan. (Nat. size.) 



,, \b. Portion of the slit-baud (enlarged). 



,, 2 Fleuroiomaria retimlata, Shy. {nat. size). Kimmeridge Clay, "Wotton-Basset. 

 The nacreous inner layer of the shell is well preserved. 

 Fig. 1 is from the cabinet of Mr. R. Damon, F.G.S., of "Weymouth, 

 Fig. 2 is preserved in the British Museum (Natural History) . 



JVote. — Mr. Robert Damon has kindly given me permission to retain his specimen 

 of Pleurotomaria Beyrichii on exhibition for two months in the table-case with the 

 fossil FleurotomaricB in Gallery B, Department of Geology. — H.W. 



II. — On Bastite-Serpentine and Troktolite in Aberdeenshire, 



WITH A Note on the Rock of the Black Dog, 



By Prof. T. G. Bonnet, D.Sc.,LL.D., F.R.S., Pres.G.S. 



IN a paper entitled " On Minerals new to Britain," ^ published in 

 the Mineralogical Magazine, vol. v. p. 1, Professor Heddle 

 mentions the occurrence of a bastite- serpentine at two localities in 

 Aberdeenshire ; one in the parish of Belhelvie, the other on the shore 

 close to a curious rock named the Black Dog. A visit to the localities 

 has enabled me to add to his account some particulars, and to offer 

 one or two corrections which seem to me not unimportant. 



Professor Heddle states that he found the rock in the former case 

 "in two quarries which are cut into a hill-side near the farms of 

 Craigie and White-Cairns, on the west side of the Belhelvie hills." 



1 Sowerby's description is as follows :—" Pleurotomaria, Defrance. Gen. char. 

 A trochiform spiral shell, with an angular sinus near the middle of the outer lip, 

 from which a band marked with lines of growth that indicate the sinus is carried 

 round the whorls ; no beak or sinus at the base of the aperture ; a columella with 

 or without an umbilicus." — (Sowerby, Min. Conch.) 



- In this paper the term mineral is used in a very wide sense, as it includes taehy- 

 lyte, Lydimi-sione, chert, lignite, spheriUite, and piichstone. If all of these are 

 minerals, what are left to us as rocks ? 



