46 JOHAN KIÆR. M.-N. Kl. 



genal spines. The segments have a markedly arched axis and geniculated, 

 furrowed pleura, that extend as short and rather sharp spines that extend 

 outwards (about the same as in Ellipsocephalus Hofft Schl.). The state 

 of preservation, however, appears to be rather imperfect, so that my 

 impression is that the finer details cannot be seen. We do not know the 

 number of the segments nor have we any knowledge of the pygidium, 

 although the latter presumably is known from a kindred form Str. strenua 

 var. nasuta Walcott^ It is only about 2.5 mm. long with a broad axis 

 that does not extend right out to the posterior margin, and is furnished 

 with 3 transverse furrows; the lateral portions are without furrows and 

 have a strongly receding anterior margin (fig. 5b). Its form reminds us 

 somewhat of the pygidium in Agraulos ceticephalus Barr-. 



MoBERG^ described the pygidium of the Scandinavian form from Torne- 

 træsk, which is of about the same age. It is very small, being only slightly 

 more than 1.5 mm. long. It is not much broader than it is long, has 

 a powerful, long, arched rhachis, narrow and somewhat arched lateral 

 parts, and a quite narrow outer margin. 



Rhachis shows 2 pairs of furrows, whilst on the other hand the pleura 

 have 3 pairs (fig. 5c). Thus it resembles neither the pygidium of the 

 Middle Cambrian Agraulos ceticephalus Bar. nor that of the corresponding 

 Ellipsocephalus forms, which as is well known have short pygidiums that 

 are markedly extended in breadth. 



A somewhat better known form is Stremiella Salopiensis Cobbold 

 from the Protolenus fauna in Shropshire. Of this form Cobbold described 

 the cranidium, the free cheeks, segments and pygidium^. 



All these segments are found isolated onl}-. As the same bed also 

 contained what is called an A)iomocarc of corresponding dimensions, it is 

 uncertain to which form the segments discovered should be referred. In 

 mv opinion, however, Cobbold's Anoniocare forms can hardly be referred 

 to the Angelins genus, but should rather be considered to belong to Strenu- 

 i'lla. They seem to me to lie very close to his Str. Salopiensis. The}' 

 mainly differ from the latter by the form of the frontal brim, but this also 

 varies greatly in the Scandinavian form. The cranidium closely approaches 

 both the American Str. strenua Billings and the Scandinavian species, 

 e. g. Str. Linnarssoni nov. sp. The}- are specially distinguished by their 



1 The fauna of the Lower Cambrian or Olenellus fauna, pi. XCVII, fig. 2 a. 



- Barrande, Syst. Silur, de la Boheme, Vol. I, pi. 10, figs. 8 — 9. 



3 As shown on page 37, the form, to which JMoberg refers the two isolated pygidiums. 



that were discovered, is either Strenuella primaeva Brøgger or an allied species. 

 -• On Some Small Trilobites from the Cambrian Rocks of Comley. (Quart. Journ. Geol. 



.Sec. Vol. 66, 1910, p. 31.) 



