DICELLOGRAPTUS. 1 t9 



Dicellograptus pumilus, Lapworth. Plate XXI, figs. 3 ob—f. 



1876. Dicellograptus pumilus, Lapworth, Cat. West. Scott. Foss., pi. iv, fig. 81. 



Stipes 1 — 3 cm. in length, widening gradually and persistently from their origin 



to a maximum breadth of "8 mm., diverging at about 3 10° from a conspicuous 



sicula ; virgella and lateral spines small, axil wide. Thecae twelve to ten in 



10 mm., overlapping half their length, narrowing aperturally, free part of 



outer wall slightly curved. Apertural margins slightly introverted, aperture 



opening within shallow excavation. 



Description. — The stipes are commonly short, not exceeding 1 — 1*5 cm. in 



length as a general rule, though longer specimens have occasionally been found ; 



they are characteristically straight, but may be very slightly curved, and the angle 



of divergence is very uniform. They measure about - 5 mm. at their origin and 



increase in width gradually throughout their extent. 



The sicula has a length of 1"3 mm. : it is as a 



Fias. 92 a and b. — Dicettoyraptu-i -jmrni- ° 



lus, Lapw. rule clearly visible between the dorsal walls of the 



stipes, but its apertural spine is inconspicuous. 



The thecse are frequently obscure, as the stipes 



have often been slightly twisted ; but Avhen seen in 



a profile their characters are clear, they are gently 



"' P of ISf en same°Tiab a^pfxx? curved > and nave tneir apertures but slightly intro- 



i>. D?tfo, 3 with complete sicula. Ditto. ' Verted ' a PP roa <* m g the Leptograpti in this respect. 



Affinities. — The small size and wide axil of this 

 species, combined with the characters of the thecge, serve to distinguish it from all 

 others at present known. 



Horizon and Localities. — Hartfell Shales. 

 Scotland : Hartfell. Wales : Conway. 



Associates, etc. — D. pumilus occurs in some abundance in the lower Hartfell 

 Shales associated with Diplog. truncatus ; the best specimens are in Lapworth's 

 collection. 



Dicellograptus angulatus, sp. nov. Plate XXI, fig. 4. 



Stipes from 1 — 2 cm. in length, very slender, and of uniform width throughout 

 their length, diverging at about 270° — 300° from a conspicuous sicula; virgella 

 and lateral spines slender, but conspicuous ; axil square. Thecal ten to eight 

 in 10 mm., overlapping for one quarter to one third their length, narrowing 



