148 C. F. ROUSSELET ON BRACHIONUS SERICUS, 



from several places in the country, by Mr. John Hood from the 

 neighbourhood of Dundee, and by Mr. John Stevens from 

 Exeter. 



In July, 1897, at the Club's excursion to Hertford Heath, I 

 found a remarkable variety of this species, in which the dorsal 

 plate extends posteriorly into a high and long projecting point, 

 as represented in Figs. 2 and 3, PI. 1 1 . 



In general appearance B. sericus resembles B. urceolaris, and 

 no doubt has before now been mistaken for this species. On- 

 closer examination, however, it will be found that the structure 

 of the lorica is very different. The whole of the lorica, including 

 the ventral plate, is covered with very fine, regular, longitudinal 

 wavy lines, which give it the appearance of " watered silk " ; 

 hence the name sericus. From certain points of view the basal 

 plate has the appearance of being pitted, which Mr. Dixon- 

 Nuttall (to whom I am once more indebted for the excellent 

 figures on PI. 11) has indicated in his drawing; but it seems 

 to me that this appearance is due to the foreshortening of the 

 wavy markings. 



The high and rounded, or more or less pointed, dorso-posterior 

 edge of the lorica overhangs the basal plate, forming here a recess 

 in which the eggs are usually carried. Anteriorly the six teeth 

 are nearly equal in length, the " antlers " being only slightly 

 longer than the outer teeth, and the sinus between them is less 

 deep than in B. ruhens or urceolaris ; the four inner teeth have 

 each a short strengthening ridge. The mental edge is ondulate, 

 with a rounded sinus in the middle. The foot opening is rounded 

 or conical in shape in the ventral plate, and square in the basal 

 plate on the upper side. 



The greatest variation occurs in the dorso-posterior edge of the 

 lorica, which, whilst always overhanging, may be simply rounded 

 or prolonged into an obtuse point ; or again, as in the Hertford 

 Heath specimens, it may be extended into a very considerable 

 pointed prolongation (Figs. 2 and 3), which gives these animals a 



