86 J. MURRAY 



of E. islandicus (18). A very few species are said to have no surface markings 

 whatever on the plates. 



The lumbar plate, which covers segment VI., or V. + VI. when these are joined, 

 is nearly always divided by two lateral slits into a sort of trefoil. Often the middle 

 and lateral flaps thus produced are bent downwards at an angle to the small median 

 portion of the plate, which is then said to be faceted. The angle joining the two 

 slits has caused it to be supposed that the posterior " tail-piece " thus separated is a 

 distinct segment, and it has also been supposed that the portion in front of the slits 

 is homologous with segment V. This is undoubtedly not the case, as when V. and 

 VI. are separate, VI. is trefoliate in the usual way. A number of species have been 

 figured without a trefoliate "lumbar plate" \_E. sintsbergensis, Scorn field (45), and E. 

 bisetosus, Heinis (7) ]. Personally I have only seen one species in which the lumbar 

 plate is not trefoliate (E. intermedium, described in this paper, see Plate XVI. Fig. 17, 

 and Plate XX. Fig. 52). In other cases I do not take the evidence of figures, unless 

 the authors refer to the character in their descriptions, as in certain positions the slits 

 are hidden and may be overlooked. 



The processes connected with the plates are either setce, longer or shorter spines, 

 little spicules, or blunt cones or knobs. Certain processes often occur in definite 

 situations, easily indicated in descriptions. Near the mouth there are four cirri and 

 two palps, which are in most species of no distinctive value. In a few species they 

 are conspicuously large, or slightly modified in form [considerably in E. cornutus 

 (34)]. In one or two species they are stated to be lacking [E. imberbis (38)]. 



Of most regular occurrence are the five lateral processes and two dorsal processes, 

 on each side. Richters distinguishes the lateral processes by the letters a, b, c, d, e, 

 (Plate XVI. Fig. 14)* counting from the head backwards. is the head seta, the 

 only process present in every known Echiniscus. It is situated at the base of the 

 head, between I. and II. The pair commonly curve forward, and look very like 

 cow's horns, but very thin, except in E. cornutus, where the resemblance is perfect. 



At the base of seta a there is generally (perhaps always) a little triangular or 

 cylindrical palp or " Auricle " as it may be called. It is rarely distinctive but in a 

 few species is of characteristic shape or large size. 



In a few species there are other processes besides these most common ones. The 

 most frequent are little spicules on the posterior borders of the plates of segments 

 II., III., and IV. between the lateral and dorsal processes. In such cases there may 

 be a similar spicule beside the slit in the lumbar plate, close to seta e, if that be 

 present. There may be more than one spicule between the lateral and dorsal 

 processes, especially on segment IV. (plates of the second pair), where there may be 

 two or three [E. oihonnce, Heinis (9)]. 



The dorsal processes usually spring from the postero-dorsal angle of the paired 

 plates, that is, at the angle marking the limits of the space occupied by the median 



* Seta e is not present in the species figured. 



