412 Quarterly Journal of Cottclwlogy. 



moUusks of South Africa and the West Indies, has given me the 

 names of two species which he has seen suspended by a thread, 

 "very thin but exceedingly strong and silk-Uke, issuing from 

 between the operculum and outer lip." Their names are Chon- 

 dropoma pUcatuluiu, Pfr., found at Puerto-Cabello, "thread y'l to 

 i4-inch long," and Tudora megaclicila, P. & IM., found at Cura^oa, 

 " thread much shorter;" 



Chond>v_poma dentafu?n^^' Say, Florida, has the same habit. 



Mr, William Nelson, who is an accurate observer of the 

 habits of the mollusca, tells me that Mr. John Dixon, of the Leeds 

 Infirmary, has seen several individuals of Clausilia rugosa var. 

 dubia, suspended. 



Pectinibranchiata. 



Bylhinia tcntaculata. — This snail suspends itself by a thread, 

 after floating, which is usually attached to the surface of the water. 



Rissoa parva is 'well known to conchologists as a thread-spin- 

 ner. Dr. J. Gwyn Jeffreys thus pleasantly speaks of it : — " Tying 

 on a rock, by the brink of a seaweed-covered pool left by the 

 receding tide, it is no less pleasant than curious to watch this 

 active little creature go through its different exercises, — creeping, 

 floating, and spinniiig''' 



The following species ci Rissoa striatula^R.cancellata, R. ahhys- 

 sicola, R. memhravcaea, R. vitrea, R. pulcherrima ; also Odostouiia 

 Warreni, Barleeia rubra, Euliuta intermedia Ceriihium refiailatum, 

 Cerithiopsis tubercularis, and Pleurotoma nebula. An account of 

 their different modes of procedure will be found in Dr. Jeffreys' 

 Avork, under their several headings. 



Litiopa, a genus of small mollusks living on the Gulf-weed, 

 are said to use a mucus filament for the purpose of regaining their 

 station, after being swept off the weed. Their method of pro- 



*■ L. and F. W, shells of N. America, part iii, p. 96. 



