'2-iO Analyses of Boohs. 



found in brackish water on the shores of Gothland and Scania, and 

 L succinea in the sea near Trelleborg. The Neritinse are fresh 

 water shells, yet N Viridis is a marine species at Martinique ; N 

 crepidularis in salt water lakes ; N meleagris amphibious ; Nauri- 

 cu/a. at Bourbon ; N Pupa probably in the sea ; Melania amarula, 

 Mfasciolata, M lineata fresh water in India; M Oweni brackish 

 water. 



3. The Aplysia dolabrifera occurs in almost fresh water in 

 marshes in Bourbon; Ccriihium sulcatum brackish water ; Ceri- 

 thiinn rcticulatum fresh water of Florida Keys ; Bulla Hydates 

 brackish pools in Chili ; B fuviatilis mud of the Delaware; Lit- 

 torina fusca ( Paludina Pjeif) and L naticaides fresh water. 



4. Tettina solidula occurs in the brackish water of the Baltic; 

 Mya margaritifera in nearly fresh marshes in Bourbon; Mya 

 armaria high up in rivers ; the common oyster, it is said, can flourish 

 in fresh as well as in salt water ; a large group is preserved in the 

 museum of the Bristol institution said to have been dredged up in a 

 river on the coast of Africa, where the stream was so sweet as to have 

 been used to water the ship. Mr. Say found the Ncritina Melea- 

 gris inhabiting St. John's river, in E. Florida, from its mouth to 

 Fort Picolata, a distance of 100 miles, where the water is potable ; 

 M. Rang found Ncritina aurieulata in fresh and salt water ; the 

 Ampullaria ovata inhabits Lake Mareotis and fresh water lakes in 

 the oasis of Siwah. The common cockle (Cadiuin edulc) is observed 

 in the ditch of brackish water at Tilbury Fort. 



From these facts Mr. Gray concludes that the general rules, which 

 have commonly been regarded as decisive of the localities inhabited 

 by recent shells, and of the nature of the deposits in which the fossil 

 species are found, cannot safely be employed for practical purposes 

 without considerable reservation. 



II- — Principles of the Differential and Integral Calculus fami- 

 liarly illustrated, $c. By the Rev. William Ritchie, LL.D., 

 F. R. S., &c. 12mo. Taylor, London, 1836. 



Those who are about to enter upon the study of this branch of 

 the mathematics are indebted to the author of the treatise before us, 

 for a boon which only those who have had to labour through a 

 " science of symbols and algebraic formulae without any illustration 

 or practical application," can sufficiently appreciate. An attempt to 

 adjust a science to the level of ordinary capacities might be made 

 without success, unless the writer possessed a thorough knowledge of 

 the subject, and the rare ability of penetrating into the causes which 

 obstruct the reception of a new study in the human mind. Dr. 

 Ritchie has shewn, not only in this work, but in many others, that 

 he is endowed with both of these qualifications in a remarkable de- 

 gree : and it is always a pleasant subject for contemplation to observe 

 a philosopher anxiously interested about the progress of his successors, 

 and at the same time instructing his contemporaries. The present 

 work cannot fail to encourage the student to study the important 

 science of which it treats, instead of filling him with " the doubts of 



