Om svenska silurcirripeder 



7 



som Barrande kallat »valve fenestrée», anföres här under namn af »cancellated 

 plate» eller »reticulate plate». Redan häri skulle man knnna se en antydan om 

 att denna Turrilepas scotica och Barrande's PI umulit es -artev tillhöra samma genus. 



En annan, Turrilepas scotica närstående, art, T. Peachi, beskrefs 1880 af 

 Etheridge och Nicholson Flera af de hithörande exemplaren visade ett ej obe- 

 tydligt antal fjäll i relativt föga rnbbadt inbördes läge. Författarne påpeka sjelfva, 

 att man här jemte korta breda fjäll rinner en serie randliggande fjäll, tillhörande 

 den typ man plägat kalla drakformiga; likheten med Barrandes Plumulites Bohé- 

 miens framhålles. Ändtligen erhölls genom Cowper Reed 2 , som 1908 underkastade 

 allt tillgängligt material af Turrilepas Peachi Eth. jun. et Nich. och närstående 

 former en noggrann revision, mera ingående kännedom om den sagda artens byggnad. 

 Då mig tillgängligt material inskränker sig till isolerade fjäll, anser jag lämpligast 

 att, hänvisande till de å vår tarla I, fig. 7 — 11, återgifna af bildningarna, här orda- 

 grannt anföra den af Cowper Reed (1. c, p. 523) lemnade beskrifniugen : 



»Definition. Body elongated oval, bilaterally symmetrical; dorsal side gently 

 convex subcarinate longitudinally, composed of two lateral series of large plates ar- 

 ranged in pairs and two median rows of small plates in contact in median line, 

 and also in corresponding pairs. Shell thin, calcareous. Lateral plates kite-shaped, 

 slightly curved, with pointed apex, hut varying somewhat in shape according to 

 their position, with their longer axes making nearly a right angle with the median 

 carina of the body in the posterior part of the organism, but becoming less and 

 less steeply inclined anteriorly till they lie nearly parallel at the anterior end. Sur- 

 face of lateral plates marked by narrow submedian fold along their length and 

 usually a narrower, less impressed one on their anterior half, both appearing as 

 grooves on the outer surface and as ridges on the inner surface of the plates; [the 

 most anterior pairs may have an anterior submarginal and a posterior submarginal 

 narrow fold in addition to the submedian one, which is always the strongest]. 

 Surface of plates crossed by regular transverse equal, closely placed and equi- 

 distant, imbricating lamellre at right angles to main fold and meeting the anterior 

 edge at a large angle, but curved forwards sharply towards the apex near the po- 

 sterior edge of the plate and more closely crowded together. Apex of lateral plates 

 more or less convex ; base broadly rounded, convex. Base of opposite lateral plates 

 nearly in contact. Successive plates overlap from behind forwards for about half 

 their width, but their apices are free. 



Median plates arranged in a double longitudinal series, with their inner edges 

 in contact along carina of body. Shape of plates short, broad, subtriangular, with 

 sinuated rounded base, long hypotenuse, more or less arched perpendicular; apices 

 directed forwards and overlapping considerably from behind forwards. Surface of 

 plates marked by one or two low submedian longitudinal folds from apex to base 



1 Nicholson and Etheridge. L. a. c. Fasciculus III. Pag. 301, pi. 20, fig. 8—10. 

 a Cowper Reed, R. The structure of Turrilepas Peachi and its allies. Transactions Roy. 

 Soc. Edinburgh. Vol. 46, part 3, n:r 21. 



