^O .lOMAN KIÆR. M.-N. Kl. 



Tcssini zone in Oland and in Nerike ^ Remarkably enough, the last two 

 appear to be the least modified. In E. granidatns Lnrs. the occipital ring 

 is still well marked and the lateral furrows of the glabella distinct, whilst 

 in iiuitkus Ang. they are indistinct, the form of the glabella in the latter 

 seeming more Streimclla- \\k(t than in the former-. The free cheeks do not 

 appear to be known, nor is the number of segments and the pygidium. On 

 the other hand some segments were found of El. graiinlatus Lnrs It is 

 interesting to note that these end in small and slightly deflected spines. 

 The latter evidently corresponds to the little pleural spine in the Lower 

 Cambrian Strciiuclla and Ellipsoccplmliis forms, but is even more strongly 

 reduced. (Textfig. 6.) 



In the case of the somewhat older E. polyto)uus Lnrs.. which is fully 

 known in an excellent state of preservation, these spines have almost 

 disappeared. Linnarsson does not mention them in connection with this 

 species, but in specimens in the Palaeontological Museum at Kristiania from 

 Oland, however, they can be clearl}- seen in the middle and posterior 

 segments as extremely short spines that might easily be overlooked. In 

 this form the cranidium is further differentiated in an EUipsoccphalide direc- 

 tion. The occipital ring has almost disappeared, the lateral furrows of the 

 glabella can no longer be seen, and the free cheeks are rounded without 

 spines posteriorly. Unfortunatety we do not know how this feature has 

 been in the Lower Cambrian species, but there is strong evidence that 

 thev had genal spines like the Strcnuella forms and the Middle Cambrian 

 El. Gcnuari. The pygidium has the same characteristic short, broad, 

 extended form as that seen in El. Hoffi Schl., to which species the former 

 is closely allied. The number of segments is 14. 



It is but a short distance from this form to El. Hoffi Schlotheim, 

 the most typical and earliest known species of the genus from Bohemia. 

 As stated above, the difference between this form and El. polytomus Lnrs. 

 is not very great. The occipital ring, however, has generally quite disappea- 

 red, and anteriorly the glabella is more sharply pointed, with a slight 

 contraction between the eye-lobes, the number of segments is reduced to 

 12, and the pleural spines have quite disappeared. (Textfig. 6.) 



Although our knowledge of these ancient forms is still imperfect, we 

 seem entitled to assume a development from primitive forms resembling 



1 Linnarsson. Öfversigt af Nerikes Öfvergangsbildningar. (Öfvers. Kungl. Vet. Akad. 

 Førh. 1875, No. 5) and Om faiinan i lagren med Paradoxides Ölandicus iGeol. Foren. 

 Stockh. Förh. 1877, No. 40.1 



2 „Tydeligt utbildat nackfàra, inga eller otydelige sidefäror ä pannan, hvilken framtill 

 tyckes afsmaina nagot mer och jevnare an hos E. polytoiuns och graiinlatus" (Linn-vRS- 

 soN op. cit. 1877 pag. 151. 



