48 LINDSTRÖM, VISUAL OEGANS OF THE TRILOBITES. 



Calymmene Bkogn. 



In the following species of this genus hypostomic tubercles have formerly been 

 recorded. 



Cal. Blumenbachi Salter Monogr. pl. 8, tig. 9. The identity of the species is 

 dubious. 



Cal. duplicata Salter Mun. pl. 9, tig. 22. The tubercles rather more linear and 

 approximated than in the subsequent. Salter calls them »two small transverse lobes . . . 

 forming ;i nearly continuous ridge». 



Cal. tuberculata Ängel. Tab. XIX tig. 5 c from the inside. 



It is remarkable that the eyes or that part of them where the cornea and the 

 lenses should be found, has been destroyed and entirely löst in all specimens of the 

 Calymmenae known to us, many hundreds having been searched and every one with a 

 lacuna on that spöt. It must have been of an excessive thinness. We know only of one 

 instance, the Bohemian Calym. Arago, in which Barrande has seen the eye intact and 

 pro vid ed with a small number of about eleven sphserical lenses. 



Calymmene intermedia Ldm. 



Pl. III figs. 6, 7. 



The clypeiform hypostoma is divided in two tields, one anterior larger, in the 

 centre elevated in a short, blunt knob, and a posterior, bearing the two elevated rounded 

 maculae, just below the semicireular groove which separates it from the anterior tield. 

 These tields are surrounded by a large börder which is posteriorly emarginated through 

 a short rounded sinus. The surface is entirely eovered by small semiglobular wartlets 

 perforated by a straight pore or duct, which being filled with a black mineral, probably 

 iron pyrites, gives a peculiar and eharacteristic aspect to the sections. In the same man- 

 ner the whole mäss of the hypostoma is pierced by straight, black lines, also filled up 

 pores, starting from the outside and ending before attaining the inner surface. 



The maculae are prominent, separated from the hypostoma through narrow, distinct 

 grooves, ovate, with the pointed end directed obliquely outwards, against the margins of 

 the hypostoma. They are eovered with wartlets and leaving only a little oblong spöt 

 free, quite smooth, this being consequently the macula proper. But in a longitudinal 

 section there is not the least distinction between this macula and the other hypostoma, 

 only, that it is free of pores. 



Calymmene tuberculata Bklnnrti. 



Pl. III figs. 8, 9. 



We have succeeded to prepare a horizontal section of the macula. This is oval, 

 perfectly hornogenous and without any strueture proper, showing only indistinctly a 

 mottled medley of påle, brownish spöts in the clear mäss. There is in both niaciil;e a 

 small darkj angular spöt placed in their inferior part, (ig. 9. 



