A HISTORY OF DURHAM 



being subtriangular, but in the latter suboval and longer in relation to the non-salient portion 

 of the third joint.' Earlier authors have noticed that in the former species the tips of the 

 bifid rostrum are slightly divergent, but not so in the latter. 



The Oxystomata are so named not from tiieir sharpened or narrow fronts, but from the 

 narrowing of the oral cavity. This buccal frame or cndostomc in the other three tribes is 

 more or less quadrate, but here it becomes triangular. In all it is more or less closed on the 

 ventral surface by the third maxillipeds, which when their inner edges meet block out of view 

 the other mouth-organs, namely, the mandibles, first and second maxillae, and first and second 

 maxillipeds. All these parts though lost to sight should be to memory dear with every student 

 who is desirous of understanding or of improving the classification of the Malacostraca. 

 Norman's dredging list for 1864 provides the Durham coast with two species of one genus 

 from the Oxystome family of the Leucosiidae, these being Ebalia tubetosa (Pennant) and 

 E. cranchii, Leach. MM. A. Milne-Edwards and E. L. Bouvier distinguish the latter from 

 the former as having the carapace less inflated, more regularly hexagonal, the front more 

 advanced, and the antero-lateral margins entire, not as in the other species having a very 

 characteristic fissure between the hepatic and the branchial regions.' 



The Macrura, or long-tailed Decapods, are in much closer relation to the Brachyura 

 than a man might suppose who was offered for his meal a choice between the tail of a crab 

 and the tail of a lobster. Lithodes maia (Linn.), the northern stone crab, recorded from the 

 Fame Islands by Mr. Tate and from Lindisfarne by Dr. Johnston, is not a true crab, though 

 it is deceptively like one. It has a short uneatable tail, and yet anomalously belongs to the 

 Macrura. But it is the special mark of a Macruran to have appendages on the penultimate 

 segment of the pleon, and of these Lithodes is destitute. On the other hand this tail-piece 

 is conspicuously unsymmetrical in the female. This and other characters make it probable 

 that the form has been evolved from among the hermit crabs, from hermits that have been 

 unable to find a hermitage. In the struggle for existence it is likely enough that such 

 unsheltered vagrants would have recourse to folding their tails for protection under their own 

 bodies. Of ordinary hermits Pagurus bernhardus (Linn.) is recorded by Mr. Tate from the 

 Fame Islands, by Dr. Johnston from Lindisfarne, by Dr. Norman from the Durham coast. 

 The last author mentions with it in his Durham dredging lists for 1863 and 1864 P. pubescem, 

 Kroyer, and P. /avis, Thompson. The first two species are now placed in the genus 

 Eufiagurus, the third in Anapagurus, the latter genus being distinguished from the former by 

 the presence of a short curved appendage at the base of the fifth leg on the left side in the 

 male. Eu. pubescens is discriminated from Eu. bernhardus by the greater slenderness of the hand 

 in the larger cheliped, which is usually on the right, and by the strong pubescence of the 

 ambulatory limbs. 



Porcellana hngicomis (Linn.) is recorded by Mr. Tate from the Fame Islands, and 

 Mr. Meek mentions the capture of ' a specimen from 4 miles off Seaham, 9 September, 

 1897.'' This little smooth species, with a flat, nearly circular carapace, scarcely a quarter 

 of an inch in diameter, and its tail doubled up beneath it, looks remarkably like a crab. 

 But an inspection of the tail shows the macruran mark, appendages to the penultimate 

 segments, well developed. Between this and the common shore species, P. platycheles 

 (Pennant), Professor Bouvier has pointed out a singular difference, namely, that in the latter 

 the nerve-chain is confined to the thorax or trunk as in the true crabs, while in P. longi- 

 cornis it runs all along the pleon, as in the lobster-like Galatheidae* Of this family 

 Mr. Tate reports Galathea strigosa (Linn.) from the Fame Islands, and Mr. Meek records 

 Munida rugosa (Fabricius), 'a splendid male specimen from near St. Mary's Island caught 

 in crab pot, 28 April, 1900.'^ The latter species is remarkable for its very elongate chclipcds. 

 The specific name given it by Fabricius in 1775 takes precedence of the synonymous 

 Astacus Bamffius, Pennant, 1777, and Munida Rondeletii, Bell, 1853. 



Turning now from the anomalous to the genuine Macrura, in which the pleon, 

 abdomen, or tail has a powerful muscular development, we find no record at present in 

 this county of the common river crayfish, though it is likely enough or almost certain to 

 occur in some of the streams. The common lobster, Astacus gammarus (Linn.), under the 

 less proper name of Homarus vulgaris, is included in the Lindisfarne catalogue by Dr. Johnston, 



1 Op. cit., xiii. 45 (Monaco, 1899). ' Op. cit., vii. 54. 



' Ncrthumb. Sea Fisheries Committee Rep. for 1902, p. 66 (1902). 



♦ Ann. Set. Nat., sdr. 7, Zoologie, vii. 93 (1889). 



* Northumb. Sea Fisheries Committee Rep. for 1902, p. 67. 



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