Notices of Memoirs — Dr. Scott — Structure of Calaniites. 73 



eyes and facial sutures suggest that it may be a larval form. Oa 

 the other hand, these features are also shown by such minute 

 trilobites as Agnostus, Microdiscus, and Shumardia ; and the lack 

 of resemblance to any of the larger trilobites of the Tremadoc fauna, 

 together with the circumstances that both specimens are minute, 

 and that the larger of the two shows no advance in organization, 

 tells in favour of the view that we are dealing with an adult 

 form. For this form I would suggest the name of Acanthopleurella 

 Grindrodi. The conformation of the head suggests Trinucleoid 

 affinities, but there is no marginal rim, and the rest of the body 

 appears to show Olenid chai"acters. Shumardia is possibly an ally, 

 but from this form Acanthopleiirella differs in the extension of the 

 glabella to the front margin of the head, in the absence of all 

 glabella-furrows with the exception of the neck-furrow, and in the 

 spinous prolongations of the thoracic pleuree, and in other respects. 



IfTOTICES OIF DVniBIvrOIDRS- 



I. — On a Primitive Type of Stkucture in Calamites. By D. H. 

 Scott, M.A., Ph.D., F.R.S.^ 



PALiEONTOLOGICAL research has afforded evidence that the 

 Horsetails and Lycopods, groups now so distinct, had a common 

 origin. The class Sphenophy Hales, restricted, so far as we know, 

 to the Palaeozoic epoch, combines in an unmistakable manner the 

 characters of Equisetales and Lycopodiales, while at the same time 

 presenting peculiar features of its own. Broadly speaking, it is in 

 the external morphology and in the reproductive structures that the 

 Equisetales are approached, while the anatomy has an evidently 

 Lycopodiaceous character. 



The synthetic nature of the Sphenophyllales, indicated clearly 

 enough in the type-genus Sphenophylinm itself, comes out still 

 more obviously in the new genus Cheirostrohus. Here the 

 general morphology of the strobilus, the form and structure 

 of the sporangiophores and of the sporangia themselves, are all 

 of a Calamarian type, while the anatomy of the axis is as clearly 

 Lycopodiaceous in character. 



So far nothing has been found to bridge the gulf which separates 

 the anatomy of the Calamarieee (Paleeozoic Equisetales) from that 

 of the Sphenophyllales or the Lycopods. The most ancient known 

 genus of Calamariese — ArcJiceocalamites — approaches the Spheno- 

 phyllales in the superposition of the foliar whorls and in the 

 dichotomous subdivision of the leaves, points on which Professor 

 Potonie, especially, has laid stress. Anatomically, however, according 

 to the researches of Dr. Renault and Count Solms-Laubach, it was 

 an ordinary Calamite, differing in no essential respect from those 

 of the Coal-measures. The stem of Arcliceocalamites, like that of 

 its later allies, had a large pith, surrounded by a ring of collateral 

 vascular bundles, the wood of which, primary as well as secondary, 



^ Eead before the British Association, Section C (Geology), Glasgow, Sept., 1901. 



