144 Correspondence — >S'. >S'. Buckman. 



the Durness fauna) and the dark outer layer of the siphuncle in 

 certain forms of Vaginoceras suggested a different chemical com- 

 position, but I could not get a molybdate precipitate. My 

 observations did not support any of the previous explanations 

 of the function of the siphuncle, including those given by such 

 careful observers as Professor Blahe and Dr. Willey, though there 

 was no need to go into them all again. 



I may also mention that I would consider the typically regular 

 septation of Cephalopoda as a whole and formation of chambers 

 filled with gas (as contrasted with the tabulation, etc., in other tabular 

 oro-anisms) to be more or less impossible without the posteriorly 

 attached siphuncle ; also that there may be a connexion between 

 the attachment (in Ammonoidea) to the inflated beginning of the 

 siphuncle or ca3cum (itself attached by one or more bands, the so- 

 called prosiphon) and the progression of the end of the protoconch 

 (in phylogeny) from asellate and latisellate to angustisellate, as 

 opposed to the reverse tendency of the following suture-lines to 

 deepen the external lobe. But these suggestions will be difficult 

 of demonstration. 



In conclusion, I hope that since several siphuncular structures, 

 notably " Grand] can's membrane ", still remain unexplained, 

 Dr. Trueman will continue his investigations into the Ammonite 

 siphuncle. L. F. Spatii. 



[This letter was received just too late for insei'tion in the February 

 number. — Ed. Geological MAGAzmE.] 



THE GENOTYPE OF 8PIR1FER. 



Sir,— By some regrettable mischance certain errors of reference 

 occur in my communication to your Magazine. January, 1920, 

 pp. 18-20. The following corrections are required : — 



p. 19, line 5 from bottom, for " M.C. ii, pi. cclxiii " read " M.C. 

 iii, pi. cclxv ". 



p. 20, line 5 from top, for " M.C. ii, pi. cxxv "' read " M.C. ii, 

 pi. cclxv ". 



p 20, line 8 from top, for " M.C. ii " read " M.C. iii ". 



p. 20, Une 12 from top, for " 141, 142 " read " 41, 42 ". 



I may also take the opportunity to point out that Sowerby's 

 plate of Spirifer striatus is numbered in M.C. iii, " 170," whereas 

 it is intended for " 270 ". The text says " S^nrifer striatus, 

 Tab. cclxxi ", whereas it should be " cclxx ". His index corrects 

 these errors. 



I desire to thank my vigilant friend Mr. Tutcher for noting my 

 lapses. 



S. S. Buckman. 



