Mr. J. Alder on Jeffreysia and Cbemnitzia. 463 



Mr. Clark the " proboscidal muzzle," which, in his generic cha- 

 racter of Chemnitzia, we are informed " may be termed an involute 

 and evolute contractile proboscis." Not veiy appropriately, one 

 would think ; for this organ, the mentum of Loven, is perma- 

 nently exserted, and attac-hed to the foot for the greater part of 

 its length. How therefore it is to be called " involute and evo- 

 lute," or can be said to be " emitted," or from whence, I cannot 

 tell. Such an attempt to adapt M. Loven's words to an organ 

 they were not intended to describe, renders this generic cha- 

 racter quite unintelligible. 



But to proceed to the quotation given from Loven's characters : 

 " Proboscis sub basi vibraculorum recondenda, involvenda ; evo- 

 luta cei-vicem latitudine vix cedens." This to most people would 

 imply a retractile and extensile proboscis. Mr. Clark thinks* 

 otherwise. He admits that " "^ proboscis recondenda' undoubtedly 

 means a retractile proboscis," but he wishes to make it appear 

 that the words ' involvenda' and ' sub basi vibraculorum' being 

 added in this genus and not in others, must make them mean 

 something else. The whole mystery of the matter however is 

 this : that the genus having been misunderstood required a fuller 

 description than others, and the latter words are evidently added 

 to show the true position of the oral aperture immediately below 

 the tentacles ; former authors, and more recently Mr. Clark 

 himself, having placed it below the mentum. But then it 

 is also said that " when unrolled it scarcely yields to the 

 neck in width." " The last observation is very important," 

 Mr. Clark informs us, " because if the proboscis is a retractile 

 one, it would be physically impossible to satisfy M. Loven's 

 phrase." [Why so ? The proboscis is not broader than the neck, 

 and the great contractility of these parts is well know^l.] " If 

 this," it is added, " is the true construction of his characters, it 

 supports those of D'Orbigny" (Lowe?), "and it would show 

 that the Chemnitzian animal has not a long retractile proboscis 

 as Mr. Alder states, and if not so, Chemnitzia would appear to 

 differ from Eulima, which has a retractile proboscis." Such is 

 the conclusion an-ived at. But why, when the length of this 

 organ is in dispute, is not the whole of M. Loven's description 

 given ? Why is it abruptly broken off at a point where the veiy 

 next words would give us the information we wish ? They ai'e 

 these : — " longitudine pedem sequans 1. superans." Surely this 

 piece of information is as important as the width on which so 

 much stress is laid. We now find that the extended proboscis 

 equals or exceeds the foot of the animal in length ; so that it is 

 evident this organ cannot be the supposed muzzle, or mentum, 

 which the former part of the description has been made to 

 represent. Besides the mentum is described separately. The 

 entire description of the two parts is as follows : — " Proboscis 



