70 Mr. T. H. Witl.crs on 



Stramentum expunsui/i, Withers, sp. 



haworthi, Williston, sp. 



• Iffvissimum, Zittel, sp. 



macadnmi, Wyville Tliomson, sp. 



pnlcheUuin, G. B. Soworby, jun., sp. 



, G. B. Sowerby, sp., var. giyns, Fiitscb. 



-, G. B. Sowerby, sp., var. minor, Fritscli. 



sijiidcnni, Dames, sp. 



tubulatum, W. N. Logan. 



Without an examination of the ''p'^ci mens, it is impossible 

 to <k'dnce from the ])nblishe(l clcscriptions and their inade- 

 quate figures wliether all of the a))ove are distinct s[)ccies 

 and varieties. It has, however, been ])ossible to examine 

 tlie type-material of (S^. pnlchelliim and «S. danvini, with the 

 result ih.'it no justification appears for consideriiinj S.dtrunni 

 to be distinct from S. pnlchellum. The distinctions given by 

 Dr. H. Woodward are " mnch greater size and more remark- 

 able capitulum " and "the form of the scutum and the 

 latera.'' Apart from the fact that all the specimens came 

 from the same horizon and chalk-pit*, what difl'erenccs are 

 seen in the scutum appear due to the age and degree of 

 development of the valve (see p. 73), and even the two 

 S|)ecimcns of L. daririni differ in this ])articular. No 

 distinct differences are- apparent to nie in the latcra, and if 

 by "more remarkable capitulnm" Dr. Woodward means in 

 the greater obliijnity of the summit of the peduncle, it must 

 be pointed out that this is accentuated in that ])articular 

 specimen merely because the scutum and upper laleia have 

 been slightly displaced and puslied down on to the npj)er 

 scales of the peduncle (see PL 111. fig. 2). S. danvini is 

 therefore regarded liere as a synonym of S. pulchellwn. 



With regard to the holotype of S, macadami, Prof. Gren- 

 ville Cole very kindly took considerable trouble to find out 

 for me its whereabouts, and recently informed me that it is 

 preserved in the Belfast Public Art Gallery and jMusenm. 

 The Curator, !Mr. Deane, most kindly lent me the spccinien, 

 and an examination of it shows no characters by which it 

 can be separated from S. pnlcltellum. Prof. Thomson stated 

 in hisdescri])tion " One specific distinction is very evident, — 

 the fusion of plates corres])onding to the scutum and the 

 scutal latus in the ujjpcr rows of the peduncle." I cannot 

 \inderstand this statement for the reason that none of the 

 j)eduncular plates are fused, but, on the contrary, have pre- 

 cisely the same structure as in the several specimens of 



* See G. E. lUbley, 1018, I'roc. Ciool. Assoc, vol. xxix. pp. 70, 87. 



