I I! K 



SOI 



THE 



In tlu-lr breadth, a compared with 



lh and thickness, tin \ ween 



i I'iihr-miurtu plaiyodon ; hut 



.Mttl long' 



.roach tin- t'oini characteristic ol" tin 1 



.?,/... FlOIll these tcetll llOWCVer 



ill, -r in :' pression, and in 



:it contraction at tin- base of Hie crown ; I therefore 



indicHlr the genus, of which, as yet, only the teeth are 



known, by the i " ii/i//. and the species from 



kshir* Muni-loin > hy the name of Ctadyodnn 



uiiony ol' the friendly aid ol' Dr. Lloyd of 



iington, to whose /.calous co-operation I owe the ma- 



for the description of the teeth of tin- present genus, 



and the Mill more rnnarkahlr ones of the British species 

 tiyrinth'xti'H. with which tin- teeth of the Clattyodon 

 are associated. 



In conclusion. Professor Owen refers to a tootli of Clu- 

 ilyotl ,i> figured hy Mr. Murchison ami Mr. Strickland in 

 thoir paper on the Warwick sandstones. (Geol. Tram., 

 2)id series, vol. \. 



TlIKi'nso MATA. M. de Blainville'* name for his first 

 family of Aporobranchi'ita, \\w first onlcr of his second 



ii of his second subclass (Paractpkoloptiora U- 

 The Aporobranchiatu, according to It. <le Blainvillc, 

 ~t of those Malacosaria, or Mollusks, which have the 

 hody of a slightly variable form, but constantly provided 

 with" natatory appendages which arc equal and lateral, with- 

 out any foot properly so called, and which often have the 

 crgans of respiration but little evident. 



Tin- following genera are arranged by M. de Blainville 

 under the family of Ttiecosomata : 



//y<i/-u .- Clfodora. divided into two sections; 1, de- 

 pressed specs. -. 1 \ . rifodora, Broiririi ; 2, conical and not 

 depressed species (genus I'uginella, Daud.), Ex., Vaginrlla 

 depresta; Cymiintiii : and Pyrfo (fossil). 



Tlie principal forms of this family arc treated of under 

 llu- article Hy.\L.tu>.t:. 



Mr. J. E. Gray, who makes the ZXecofOMOftl the first 

 order of the class i-Jth) PTEHOPODA, divides the forms which, 

 in his opinion, should be arranged under that order, into 

 the following families and genera: 



Fam. 1. Cleodoridae. 



Genera : Hyaltca ; Diacria ; Cleodora ; Balantium ; 

 Pl-uropui ; I "ngiiiclta ; Creseis ; Brocfius ; Psyche ; Eu- 

 ribia. 



Fam. 2. Liniacinidae. 

 Genus, Limaciiia. 



Fam. 3. Cuvierida-. 

 Genera: Cttri/ /in : Trii<trres. 



Fain. I. < Ymbuliadae. 

 ais, Cymbuliii. 



THKDKN. .lOHANN CHRISTIAN' ANTON, a cele- 

 brated Gei man surgeon, was born Sept. 13, \7\4, at Stein- 

 In-ck, a small village not far from Wismar, in the duchy of 

 Mecklenburg. His family had been mined by the dis- 

 asters of war, and his father died when lie was young. \\liieh 

 two melancholy events had an unfavourable influence upon 

 his education and his first enhance into life. Hi' hail 

 liartll. 1 the bare clement.-, of education, when, at 



the age of thirteen, he was reduced to the necessity of 

 hiring himself out as a servant ; but this occupation was 

 so revolting to his feelings, that lie determined to learn a 

 trade. Accordingly his elder brother, who was a tailor, 

 '.cd him a-, an apprentice: but Thcden did not find 

 this employment more suited to his taste and talents 

 than his former one, and, as he got nothing but reproofs 

 liom his brother, he finally determined to devote himself 

 to the study of medicine. He wa-. first place d by his friends 

 with a surg( mi at liutzow, where lie spent four years in a 

 barber's shop without any real advantage ; and as soun as 

 his apprenticeship was finished, he went to Rostock, Ham- 

 burg, Lfibedf, and Danzig. Ill lhi> la-t city he at length 

 ! in obtaining some employment in the troops of 

 the king of Prussia, and was attached as surgeon to a 

 Miuadron ol iimasMcis. The zeal and punctuality with 

 which he performed all hi.-> duties in thi.-. | ::ained 



him the eMceni and friendship of his sii|ieiior ofliecis : tlie 

 the ehict surgeon . -<ij<,r , 



Mil shown him by king 



William I. at a review t Kiesenbmg, and the 

 death of this prince put an end to all the hopes nf promo- 

 Alucli IK- IKM! ,ii first entertained. In 171:: ! . 



.111, where the celebrated Schnnrvchmidt, who jiutl> 

 apincciated hi-, talents, hiininmd him with his Inniilship, 

 and procured for him the post of chief surgeon during the 

 second war in Silt-la. At the end of I'M 

 turned to Herlin. and devoted himself witii unremitting 

 attention to the study of anatomy and suigery. The 

 Seven Years' War afterwards furnished him with num. 

 opportunities of displaying the skill that he had admired, 

 and also the excellent qualities of his heart. Frederick the 



Great raised him gradually from one post to another, till he 



became at la^ hi chief military surgeon. Thedcn, in this 

 eminent position, improved all ihe branches oft' 

 and displayed an activity which contributed still more to 

 gain him the good opinion of his -overeiirn. The sue. 

 of Frederick honoured him equally with his confid-. 

 and Theden continued to enjoy to the end of his life an 

 esteem and respect for which lie was indebted only to his 

 real merit and eminent Mrvicee. He died. October 21, 

 IT'.iT. at the age of eighty-three. The continual fatigue 

 and agitation of war did not prevent his drawing up and 

 putting in order the observations which an immense tield 

 of action had given him an opportunity of collecting. 

 His works are not numerous, but they bear the -tamp of 

 experience, and one n :n them the firm and bold 



touch of a man who did not venture to take up his pen till 

 alter thirty years of most extensive practice. From this 

 eulogium we must however except all the theoretical 

 of his writings, which, unfortunately, hold a prominent 

 place in them, and which are only based upon the founda- 

 tion of the antiquated principles of the humoral theory. 

 The following is the list of his works mentioned by M. 

 Jourdan in the ' Biographic Medieale,' from which work 

 the preceding account has been taken : N'eue Bcmer- 

 kungen uiul Ki fahrungen zur Bcreichcrung der Wundarz- 

 iieykunst mid Medicin.' Herlin and Stettin. 1771-17'.:"'. s\o. ; 

 ' Unterricht fur die Unterwundirzte bey Armeen,' Herlin, 

 1774, 8vo., and 17S2. Hvo. ; Sendschr'ciben an Kichter, 

 die neu crfundencn Catheter aus der Kesina clastica be- 

 trclfend, 1 Berlin, 1777, Kvo. 

 TIIKFT. [LAKCKNY.] 



THEIN, or Tlieiua, the peculiar principle often, which 

 was procured and analysed by M. Jobst of Stuttgard. He 

 prepared it by boiling tea-leaves in water, filtering and 

 concent i ating the solution, and adding to it acetate of 

 lead as long as precipitation occurred ; after filtration 

 the excess of lead wa> precipitated by hydrosiilphuric 

 arid, and by subsequent evaporation crystals of thein 

 deposited which possessed the following properties alter 

 purification: they were sort, acicular, snow-white, much 

 more soluble in hot than in cold water, alcohol, or tether; 

 they dissolved readily in acids, and were decomposed 

 when heated either in sulphuric or nitric acid. Thein 

 has n.ii effect on vegetable blues: alkalis do not precipitate 

 it from solution in acids, and when boiled in a strong solu- 

 tion of potash it is decomposed, and ammonia is evolved ; 

 it contains water of crytallization, which it loses at 212'. 

 Thein may be sublimed. 



According to the analysis of .lobst. thein is composed 

 of 



Hydrogen ... 



Carbon .... 49'(JO 

 Oxygen . . . IG'27 



Azote .... 28-91 



too- 



1" i e marked that this analysis very closely resembles 

 that, of Caft'ein as given by I. icing. 



THELICO'NUS. Mr. Swainson's name for a subgcnus of 



CciM's. I '\ .. ' '. ,//v iill\s,ltrltll. (Mil! 



THKLIDKKMA, Mr. Swainson's name for a subgenus 

 ofl'iiin. (Malacology.) [.NAIADKS.] 



THKI-I'DOMl'S. a form placed by Mr. Swainson under 

 nily 'irtfliitlic, in the subfamily Kntrlhiitr, with 

 . ric name at the head of this article. 

 .iple, Tlirliiltimn\ Hruzili: 



Mr. Swainson thus describes it. 'We have placeil the 



Tri: Ii nl,f next to the llrlicithe under Ihe belief that they 



followed each other, although the links of connection 



wanting. It is clear that of all the types of the Tr'n-hidrt; 



i is that which by its general form makes the 



' appioach to lii/ii : while the thickening of the 



inner lip. which r Ihe umbilicus, is found also, 



but in a 1. <-\ mail) of the land volutes, J.uccr- 



