346 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



lateral their anterior terminations at the margin, although the 

 sutures are in a condition of symphysis and do not show on the 

 specimens. Glabella subconical and divided by four transverse fur- 

 rows into a globose anterior lobe and three, narrow, transverse 

 lobes ; occipital ring strong and with a minute median node ; pal- 

 pebral lobes small and united to the anterior lobe of the glabella 

 by short ridges. No traces of facial sutures. Interpalpebral ridge 

 crossed by faint furrows indicating the continuation of the glabellar 

 lobes across the dorsal furrow out into the interpalpebral ridge.' 

 The third glabellar lobe continues out into the intergenal spine. 



Thorax with seven segments. Axial lobe large, convex ; pleural 

 lobes narrow and with the third, sixth, and seventh pair extended 

 into long spines ; pleural groove strong and obliquely transverse. 



Pygidium a small plate with only one transverse furrow as far as 

 known. It is almost enclosed by the spinous extension of the pleurae 

 of the seventh segment. 



Surface marked by a very fine network of slightly raised, very 

 narrow, irregular ridges. 



The largest dorsal shield has a length of about ii mm., the greater 

 number of specimens are smaller. 



Genotype. — Olenelloides armatus Peach. 



Stratigraphic range. — Upper beds of Lower Cambrian in asso- 

 ciation with Olenelhis lapworthi. 



Geographic distribution. — Northwest of Scotland, about upper 

 portion of Loch Maree. 



Qk^r vations. — This is essentially a larval form of Olenellus. 

 ThSBBge cephalon and narrow thorax indicate this, and there are 

 additional characters to be considered, such as the spinous exten- 

 sions of the intergenal angles and antero-lateral angles similar to 

 those in the young of Olenellus gilberti [pi. 36, figs. 11-14]. The 

 glabella is conical and primitive as in Nevadia [pi. 23]. Eyes primi- 

 tive and with an interpalpebral ridge as in the voung of Olenellus 

 gilberti [pi. 36, figs. 11, 12], Elliptocephala [pi. 25, figs. 9 and 10], 

 and Pcedeuniias transitans [pi. 25, figs. 21 and 22]. The narrow 

 pleural lobes suggest the pleural lobes of the young of Pcedeumias 

 transitans [pi. 32, figs. 4-6]. The spines of the third and sixth seg- 

 ments indicate a degenerate form. 



^The interpalpebral ridge is the ridge or elongated tubercle between the 

 glabella and palpebral lobe that is formed by the extension of the three pos- 

 terior glabellar lobes. These are well shown in the young cephalon of Ellipto- 

 cephala asaphoidcs [pi. 25, figs. 9 and 10]. 



