704 



SCIENCE. 



[N. S. Vol. XIX. No. 487. 



tendency amongst both vertebrates and inver- 

 tebrates with a flattened ventral surface to 

 have the lateral or pleural margins produced 

 into processes of some sort. Cephalaspis is but 

 one of numerous instances that might be men- 

 tioned amongst fishes, and illustrations abound 

 amongst trilobites and various lower inverte- 

 brates. 



The paired condition of the marginal scales 

 in Cephalaspis is without significance, being 

 a necessary accompaniment of the flattened 

 ventral surface. Were the body laterally com- 

 pressed, we should probably find but a single 

 row of median scutes, as in Lasanius and 

 Birkenia, although even in the latter genus 

 Dr. Traquair is of the opinion that they are 

 paired. Fulcra, also, are often paired; and 

 it must be remembered that even a typically 

 impaired structure like the anal fin may oc- 

 casionally appear as double. That the struc- 

 tures called ' fringing processes ' by Dr. Patten 

 can be looked upon in the nature of append- 

 ages has been emphatically denied by Dr. 

 Gaskell,* who has studied the actual speci- 

 mens upon which our Dartmouth friend bases 

 his conclusions. Jaekel, of Berlin, likewise 

 fails to see that there is any evidence of ap- 

 pendages in these forms.f Hence it would 

 appear that paleontologists are not unani- 

 mously in favor of deriving the lateral fold of 

 vertebrates from marginal scales such as oc- 

 cur in Cephalaspis. 



Drepanaspis. — For our knowledge of the or- 

 ganization of Drepanaspis, one of the most 

 interesting Paleozic fishes brought to light 

 within recent years, we are indebted almost 

 exclusively to the dean of British paleichthy- 

 ologists. Dr. R. H. Traquair. In an apprecia- 

 tive review of Traquair's recent memoir on 

 the ' Lower Devonian Fishes of Gemiinden,' 

 published in no. 471 of this journal, J Dr. 

 Bashford Dean takes issue with the original 

 author regarding the orientation of the crea- 

 ture. It is stated by Dean that Traquair's 

 reasons ' seem inadequate for distinguishing 

 dorsal and ventral sides. In no specimen 



* Journ. Anat. amd Phys., Vol. 37, p. 198, 1903. 

 t Zeitsehr. deutsch. geol. Ges., Vol. 55, p. 84, 

 1903. 

 t Science, Vol. 19, p. 64, 1904. 



figured is the relation of the dorsal lobe of the 

 tail shown convincingly to be continuous with 

 the so-called dorsal aspect.' 



Whatever may be thought of Traquair's 

 figures, although his plate 2 seems to us con- 

 clusive enough, there can be no question about 

 the originals, and those who have examined 

 them attentively are compelled to admit the 

 correctness of the Scottish author's interpreta- 

 tions. The dorsal ridge scales are larger than 

 the ventral, and form a more extended series, 

 beginning further forward and continuing 

 further back than the ventral fulcra. Several 

 specimens in the Edinburgh Museum have 

 been pointed out to the present writer by Dr. 

 Traquair in which this row of prominent ridge 

 scales can be traced continuously from a point 

 shortly behind the median dorsal plate to the 

 tip of the dorsal lobe of the tail. The extent 

 to which the caudal lobes are covered with 

 fulcra is well shown in PL 4 and PL 1, Fig. 1, 

 of the memoir in question, and their connec- 

 tion with upper and lower systems of body 

 plates appears tolerably distinct. 



C. E. Eastman. 



Cambridge, Mass. 



SPECIAL ARTICLES. 



ON THE FEASIBILITY OF MEASURING TIDES AND 

 CURRENTS AT SEA. 



The importance of measuring the rise and 

 fall of the tide, and especially the direction 

 and velocity of the current at points more or 

 less remote from land, is obvious to any one. 

 The following brief discussion of a few ques- 

 tions involved seems to show that such meas- 

 urements, although rather costly, can probably 

 be made in almost any body of water whose 

 surface at times becomes reasonably calm; at 

 any rate, it should generally be possible to 

 measure the current. 



It is here proposed to make use of a species 

 of piano-wire sounding apparatus, in which 

 the ' lead ' consists of a large stone, or of a 

 bag or box containing stones, which is at- 

 tached to the sounding wire by means of a 

 string or a finer wire. This weight when 

 once cast is to remain immovable on the bot- 

 tom and is not to be recovered. The wire 

 drawn taut serves to indicate when the vessel 



