M. A. GiardoM the Genus Entoniscus. 143 



vcrccl by Johannes Miiller in Synapta digitata, it is also 

 solidly attached to an internal organ." 



It is clear from this passage that Steenstrup perfectly 

 understood the general relations of the Entoniscus to the crab. 

 Instead of referring to the Danish text, or to the German 

 translation of Creplin, which is very correct, Fraisse has no 

 doubt spoken of Steenstrup's work only from what Lilljeborg 

 says of it. The latter (4, p. 291, 'Annales ') has, intact, con- 

 founded the Entoniscus observed by Cavolini with the Liriope 

 (now Cryptoniscus) described by Iiathke; and he has, moreover, 

 very wrongly ascribed the same confusion to Steenstrup. 



Even the learned carcinologist Spence Bate has not been 

 able to keep himself clear of several errors in the citation 

 which he makes of Cavolini's memoir*, in connexion with 

 the genus Gryptothiria, Dana. He says : — " Cavolini first 

 described and figured two different crustaceous animals (one 

 of which he doubtingly referred to the Oniscus squill ifbrmis 

 of Pallas) which he had found parasitic within a sac attached 

 to the tail of a crab belonging to the genus Portunus or Gar- 

 c&nus." There are, as will be seen, nearly as many inac- 

 curacies as words in this short reference. 



The first and only zoologist who, since Cavolini, met with 

 parasites of the genus Entoniscus was Fritz Miiller, who 

 appears not to have known the observations of the Italian 

 naturalist. It was in 1862 that Fritz Miiller formed the 

 genus Entoniscus for an Isopod crustacean which he had met 

 with in the visceral cavity of a Porcellana of the coast of 

 Brazil, and which he named Entoniscus p>orcellanw\. 



In 1871 the talented zoologist of Desterro made known a 

 new species of the same genus {Entoniscus cancrorum), a 

 parasite of several species of Xantho. 



Besides these two species, Fritz Miiller has also met with 

 Entonisci under the following circumstances : — 



1. In a small species of Porcellana which is found rarely 

 among the Sertularians and Bryozoa upon the rocks (a single 

 female of Entoniscus which could not be studied, so that it is 

 impossible to assert that it belongs to the species parasitic on 

 the common Porcellana). 



2. In a Porcellana named by Fritz Miiller Porcellana 

 {Polyonyx) Creplinii. It is allied to Porcellana uiangulata, 

 Dana {Polyonyx, Stinips.), and usually occurs in pairs in the 

 tubes of Chwtopterus. Only three times did Miiller meet with 



* ' British Sessile-eyed Crustacea/ vol. ii. pp. 262 & 204. 



t According to F. Miiller this species of Porcellana, of a blackish-green 

 colour, is excessively common under stones at Desterro. (Five per cent, 

 of these crustaceans harboured the parasite. I 



