MONOGRAPH OF THE LEUCOSIADJl. 293 



Persephona Lamarckii, Leach, I, c. p. 23. Desmar. /. c. p. 168. 

 Guaia punctata, Edw. I. c. p. 127. 

 Hab. ad insulas Antillas. 



After a careful collation of the specimens in the British Museum, I have found myself 

 compelled to come to the conclusion, that all those which had been designated by Dr. 

 Leach as of two distinct species, and named respectively P. Latreillii and P. Lamarckii, 

 are in fact specifically identical. They vary only in a slight degree in the prominence of 

 the angular ridge on the pterygostomian region; and even his own specific distinction 

 goes no further than the meagre expression, in the one case, " angulis subangulatwi dila- 

 tatis," and in the other, " angulis anticis gradatim et obtuse dilatatis." It appears that 

 all the specimens which were in the collection at that period were entirely faded, so as to 

 have lost that striking and beautiful marking which would have enabled him to identify 

 them with Herbst's figure. Browne gives no indication of these markings, either in his 

 figure or in the letter-press. It is also remarkable that Leach should have been un- 

 aware that those specimens were originally in. the Sloanian Collection, and therefore 

 brought from the West Indies. As the nomenclature has thus become confused, I have 

 ventured to change the specific name ; and retaining the generic one given by Dr. Leach, 

 have adopted for the species the name Guaia, which Milne-Edwards had applied gene- 

 rically. 



I find that in this genus, as well as in many others, the relative position of the three 

 posterior spines affords a very fixed as well as tangible specific character. In the present 

 species, the middle spine is but little higher than the lateral ones, which are very distant ; 

 whilst in Lichtensteinii the three are much nearer to each other, and form almost an equi- 

 lateral triangle. 



Persephona Lichtensteinii, Leach (Tab. XXXI. fig. 6). Testa orbiculari, angulo ptery- 

 gostomiano in dente producto, margine laterali unidentato ; spinis posticis sequalibus, 

 medio cum lateralibus triangulum sequilateralem designante. 



Persephona Lichtensteinii, Leach, Zool. Miscell. iii. p. 22. 

 Hab. ? Mus. Brit. cJ et ? . 



Carapace orbicular, depressed, sparsely granulated; the pterygostomian angle pro- 

 duced into a prominent tubercle or tooth ; another on the lateral margin on each side ; 

 the three posterior spines equal, and so placed as to form the points of an equilateral tri- 

 angle. Front broad and nearly straight. External foot-jaws with the inner stalk in the 

 male nearly plain, with only a slight longitudinal groove; in the female more deeply 

 grooved towards the inner margin. Anterior legs more slender than in the other species. 

 The arm wholly covered with small tubercles : a line of granules on the outer side of the 

 wrist. The two specimens in the British Museum are a male and a female ; unfortunately, 

 the abdomen is wanting in each. 



Length of carapace l - 2 in. 



It is remarkable that the two specimens above referred to in the British Museum are 

 the only ones known of this species. There is no figure extant, nor any account of it 

 beyond the meagre definition given by Leach in the ' Zoological Miscellany,' and which is 



2q2 



