no. 3618 GONODACTYLUS — MANNING 13 



almost straight, completely fringed with setae; both segments of 

 exopod with normal complement of setae; proximal segment of exo- 

 pod with fixed distal spine on ventral surface; basal prolongation 

 with inner spine slender, shorter than outer. 



Color. — Several specimens have dark chromatophores scattered 

 over the body, concentrated in dark patches on the sixth thoracic 

 and first abdominal somite, and in transverse bands on the carapace 

 and abdominal somites; sixth thoracic somite with dark lateral 

 patches. 



Size.— Males, TL 15.6-34.2; females, TL 16.8-31.5. Other measure- 

 ments of male holotype, TL 34.2 : carapace length 7.7; fifth abdominal 

 somite width 6.3; telson length 4.8, width 5.3. 



Etymology. — The species is named for W. F. Lanchester, the 

 carcinologist from Cambridge who was the first to recognize the 

 importance of the diversity of the structure of the telson in 

 Gonodactylus. 



Discussion. — G. lanchesteri is most similar to G. spinosus Bigelow, 

 differing primarily in the telson having well-developed intermediate 

 marginal teeth, being wider than long, and having fewer (and usually 

 larger) dorsal spinules. As in G. hendersoni, the number and arrange- 

 ment of spinules on the telson is very variable. G. lanchesteri has 

 no trace of the ventral carinas on the submedian marginal teeth of 

 the telson that are characteristic of G. demanii and G. hendersoni, 

 and the full complement of setae on the uropod distinguishes both 

 G. lanchesteri and G. spinosus from G. demanii and G. hendersoni. 



As in other species, the carinae of the telson and sixth abdominal 

 somite in males are more swollen than in females, and younger 

 specimens are more spinulose than adults. The extent of spinule 

 variation on the telson is shown in figure 4. 



There may be two species mixed in this series of specimens, both 

 of which have well-developed intermediate marginal teeth on the 

 telson. One of the specimens from Andromache Reef (male, TL 

 19.4) has many small spinules on the dorsal carinae of the telson, 

 as does the illustrated female from the type-locality. The remainder 

 of the specimens have far fewer spinules on the dorsal carinae of 

 the telson and larger spinules on the carinae of the marginal teeth. 

 I have been unable to find other differences. 



Distribution. — Western Indian Ocean, from the Red Sea to South 

 Africa. Records in the literature include Red Sea (Nobili, 1906a; 

 Tattersall, 1921; Parisi, 1922; Gruvel, 1936; Ramadam, 1936; Monod, 

 1937; Dollfus, 1938; Chopra, 1939; Parisi, 1940; Ingle, 1963); Gulf 

 of Aden (Chopra, 1939); Mozambique (Barnard, 1950); and South 

 Africa (Barnard, 1950). On reefs from shallow water to 18 fms. 



256-174 — 67 2 



