256 Part III. — Twelfth Annual Report 



antennae nine-jointed, and bearing long slender setae. The proportional 

 lengths of the joints are shown in the formula : — 



15 • 18 • 13 • 10 • 8 • 11 ' 6 • 5 • 11 • 



1 * 2 • 3 • 4 • 5 :• 6 • 7 ' 8 ■ 9 ■ • 



The secondary branches are composed of two moderately long joints. 

 Mandibles with the oblique biting edge coarsely serrate. Mandible-palp 

 with a moderately large, stout, basal part, and two small branches (fig. 16). 

 Maxilla-palp with three small narrow branches, each bearing two to three 

 slender apical setae (fig. 17). Posterior foot-jaws short, moderately stout ; 

 the last joint somewhat ovate, bearing a slender seta near the middle of 

 the inner margin. Terminal claw slender, gently curved (fig. 19). The 

 first pair of swimming-feet slender. Inner branches considerably longer 

 than the outer. The inner terminal claw of both branches is comparatively 

 very long and slender (fig. 20). In the fourth pair the inner branches 

 reach slightly beyond the second joint of the outer branches. The last joint 

 of the inner branches is about equal to three-fourths of the entire length 

 of the other two joints, and the length of the last joint of the outer 

 branches is nearly equal to that of the first and second together (fig. 21). 

 The basal joints of the fifth pair are broadly triangular, and the apex 

 reaches to near the middle of the secondary joints. They are furnished with 

 three plumose setae on the inner distal margin, and a moderately long ter- 

 minal and small sub-terminal setae. Secondary joints sub-cylindrical, and 

 bearing eight setae, — three on the inner and^three on the outer distal mar- 

 gin, and two at the apex. Both margins of both joints are fringed with cilia 

 (fig. 23). Caudal stylets very short. All the body segments are fringed 

 with cilia round the posterior margin. 



Male. — Anterior antennae apparently eight-jointed, hinged between the 

 second and third and between the fifth and sixth. The first three joints are 

 sub-equal, and the fifth and last are about equal in length to that of the 

 first three, but are narrower ; while the fourth and seventh are smaller 

 than those that preceed or follow. The inner branches of the third pair 

 in the male are provided with an elongate spiniform appendage, slightly 

 hooked at the end (fig. 22). The basal joint of the fifth pair is furnished 

 with only two small spiniform setae. The secondary branch is somewhat 

 like that of the female, but rather smaller. 



Habitat. — At Seafield, near Leith, among mud near low-water mark. 

 This species resembles Thalestris forficula, Claus, but differs in several im- 

 portant particulars, — it differs in the proportional lengths of the joints of 

 nine-jointed anterior antennae ; it also differs in the structure of the swim- 

 ming-feet, as shown by the description and figures. 



Genus Pseudowestwoodia, nov. gen. 



Very like Westwoodia in general appearance when seen from the side. 

 Anterior antennae six or seven-jointed. Secondary branch of posterior an- 

 tennae small, one-jointed. Mouth appendages similar to those of West- 

 woodia. Both branches of first pair of swimming-feet two-jointed, but in 

 general appearance the first pair resemble those of Westwoodia. The other 

 thoracic appendages are similar in structure to those of that genus. The 

 distinctive characters of Pseudowesiivoodia are the one-jointed secondary 

 branch of the posterior antennae, and the first pair of swimming-feet with 

 both branches two-jointed. All the other characters are more or less 

 similar to those of Westwoodia, hence the proposed generic name for the 

 form now under consideration. 



Considering the many points of resemblance between the characters of 

 the species now to be described and those of the genus Westwoodia, a 



