462 



MISS E. M. E. WOOD ON THE LOWER LUDLOW [May I9OO, 



Fig. 13. — Monograp- 

 tus ultimus (x5). 

 Enlargement of 

 fig. 9 b in PI. 

 XXV. 



Polypary never exceeding 2 cm. (-8 inch) in length, generally 



less than 1-27 cm. (-5 inch). Width at the proximal end = about 



•63 mm. ('025 inch), increasing gradually to a maximum of 1*6 mm. 



(•06 inch). 1 Polypary slightly curved, especially at the proximal end. 



Proximal Extremity. — Sicula long and curved, extending 



nearly to the level of the aperture of the 



second theca ; about 1*9 mm. ("075 inch) 



long and 5 times as long as wide. Ventral 



wall of aperture prolonged into a spine. 



The first theca arises distinctly above the 



aperture of the sicula. 



Thecae thirty to twenty-eight in the 

 inch (twelve to eleven 2 in 1 cm.), in- 

 clined to the axis at an angle of 30° to 

 40°. In specimens in relief the thecae are 

 of the M.-colonus type, but Dr. Perner states 

 that in compressed specimens they are 

 rather of the type of M. vomerinus or 

 M. crenulatus. Adult thecae 1*6 mm. 

 (•06 inch) long, and from 3 to 4 times as 

 long as wide, in contact only or with 

 slight overlap. Outer free wall straight or 

 slightly concavo-convex. Dr. Perner states 

 that the aperture is perpendicular to the 

 axis of the polypary ; but in all the 

 Bohemian specimens preserved in relief 

 in true profile, that I have examined, the 

 aperture is at right angles to the axis of the theca : this is the case 

 also with the English examples. 



This species is readily distinguished by 



(1) Its small size ; 



(2) Its narrowness ; 



(3) The number of thecae to the inch ; and 



(4) The form of the thecae. 



The affinities of the species are by no means clear. I have 

 placed it, however, in the group of M. dubius provisionally because 



(1) It has only one type of thecae ; and 



(2) The first theca is inclined to the sicula at a fairly low angle. 



On the other hand, the thecae possess characters which ally it to 

 M. vomerinus and M. colonus rather than to M. dubius, and the 

 relation of the first theca to the sicula is in some respects similar 

 to that in M. colonus. 



Foreign Localities. — Bohemia (Kosof, Lochkov, Dlouha Hora, 

 Kozel, Dvoretz). 



BritishLocalitie s. — Long Mountain (north side, near Frochas); 

 Lake District (Helm Knot). 



Horizon. — Zone of M. leintwardinensis var. incijpiens. 



Associate. — M. leintwardinensis var. incipiens. 



1 Dr. Perner states the width at 2 mm., but no specimens figured measure more 

 than 1*6 mnu 2 Dr. Perner says ' six,' but this is obviously a misprint. 



