Mr. W. II. Benson on the genus Tomichia. 377 



cidity is perceptible in even the thicker leaves : R. carpinifolius 

 is moreover apt to have its terminal leaflets wholly or partially 

 subdivided, so as to produce septenate leaves. These character- 

 istics are absent from the group " Nitidi," to which R. imbricatus 

 belongs. 



I may add that it flowers early, almost contemporaneously 

 with R. nemorosus, and nearly a month before its true allies. 



Trinity College, Cambridge, March 25, 1851. 



XXXVII. — Characters o/ Tomichia*, a new palustrine testaceous 

 Mollusk from Southern Africa, heretofore referred to the genus 

 Truncatella. By W. H. Benson, Esq. 



In the December number of the ' Zeitschrift fUr Malakozoologie ' 

 of 1 846 there appeared an interesting Monographic Essay on the 

 genus Truncatella of Risso by Dr. Louis Pfeiffer. In that article 

 the author complained, with reason, of the difficulty of reconciling 

 the conti'adictory statements of observers regarding the animal 

 inhabiting the shells referred to the genus, with reference to the 

 situation of the eyes, to its mode of life, and residence ; without 

 certainty on which points no positive place in the system could 

 be assigned to the group. 



On a perusal of the various statements there collected, it does 

 not appear to be an unnatural conclusion if we suppose that some 

 of the animals brought together on account of a general resem- 

 blance in their testaceous covering, belong, in reality, to different 

 genera; and that, while each of the observers may have been 

 in the right, the system has been in fault which insisted on 

 clubbing together dissimilar beings. In regard to their habits, 

 an amphibious mode of life, similar to that of Assiminia, Leach, 

 will explain most of the statements put forth, with the exception 

 of a single case in which two or three living examples of Trun- 

 catella were stated to have been found in moss on the slopes of 

 hills near Triest. The presence or absence of salt in the water 

 which they occasionally frequent appears to be immaterial to 

 several amphibious moUusks, such as Assiminia and Nematura, 

 nobis. I have observed the same indifference in some of the 

 Nerithm of Indian estuaries. 



In the paper in question fifteen species of Truncatella are re- 

 corded, and the diagnoses of fourteen are given at length. Sub- 

 sequently, in the July number of the ' Zeitschrift ' for 1847, Trun- 

 catella is referred, with a mark of doubt, to the Cyclostomacea, 

 and the following characters arc assigned to it by Dr. Pfeifi"er. 



* From ToniKos, truncate. 



