IQI5-1 Fauna of the Chilka Lake : Crustacea Decapoda. 317 



Genus PENAEUS, Fabricius (Smith). 



1906. Peneus, Alcock, Cat. Indian Decap. Crust., Ill, i, p. 4. 



1911. Penaeus, de Man, Decap. ' Siboga* Exped., I, Penaeidae, p. 95. 



De Man's examination of the type specimen of Penaeus semisulcatus , de Haan, 

 has had unfortunate consequences, for it involves an alteration in the names given 

 by Alcock to two of the most abundant Indian species of the genus. 



Alcock' s Penaeus semisulcatus, the common salt-water prawn of the Calcutta 

 markets, is shown to be specifically different from that described in the Fauna 

 Japonica and is identified by de Man (though the determination is perhaps open to 

 question) with Dana's P. carinatus. The form described by Alcock under the name 

 of P. monodon, Fabricius, is however identical with de Haan's semisulcatus: the 

 points of distinction which de Man notices (loc. cit., p. 98) between de Haan's 

 type and Alcock' s figures have no real existence, a fact which I have been able to 

 determine by an examination of Indian specimens and by comparison with Japanese 

 examples received from Prof. Kishinouye under the name of P. ashiaka. 



The description that Fabricius gave of his Penaeus monodon is insufficient for 

 its recognition ; but it was found in Indian seas and it is clear that the name must 

 belong to one of the three forms which, in de Man's memoir, are referred to as 

 P. semisulcatus , P. carinatus and P. indicus. De Man has not associated any species 

 with the Fabrician name and it is probably best that it should be ignored, though 

 the possibility that the type specimen still exists must remain a menace to the 

 stability of the revised nomenclature. 



Two species of Penaeus, P. carinatus, Dana (de Man) and P. indicus, M.-Edw., 

 are common in the Chilka Lake. They are to be found at all seasons of the year 

 both in the main area and in the outer channel and are able to exist in water varying 

 in specific gravity from i - ooo to 1-0265. 



Penaeus carinatus, Dana (de Man). 



1906. Peneus semisulcatus, Alcock (not of de Haan), Cat. Indian Decap. Crust., Ill, i, p 10, pi. i, 

 fig. 2. 



1911. Penaeus carinatus, de Man, Decap. ' Siboga' Exped., I, Penaeidae, p. 101. 



The precise meaning of de Man' s statement {loc cit., p. 102, end of para. 1) is not 

 quite clear to me. As I understand it, he implies that, should the identity of 

 Alcock' s monodon and de Haan' s semisulcatus be established, he would consider it 

 justifiable to use the name monodon for the species which he himself records as P. 

 carinatus, Dana. As stated above, I have been able to establish the identity he 

 postulates; but, now that Alcock' s application of monodon is shown to be incorrect, 

 I do not think it can safely be used for any other species. 



It is a choice of evils. As the matter rests at present , it seems to me better to 

 employ the term carinatus, as a provisional measure, and one less liable to cause 

 confusion than that consequent on a re-introduction of the name monodon in a new 

 sense and without any certainty that its application would be well-founded. Even 



