handles: anatomy of ttturitella communis. 59 



if the sinus has any connection with the slit in the Biotocardia, they 



may perhaps be considered slightly more primitive than T. communis. 



r Their raduJae, however, are of the characteristic Turritella type, and 



show no trace of accessory lateral teeth. 



, T. triplicata, Broc. [Troschel, 9] (pi. xii, fig. 12). The most interesting 



, feature in connection with the radula of this species is the presence of 



a third lateral tooth. This peculiarity, though not unique, is so 



unusual amongst the Tamioglossa as to suggest that it is a variation 



( devoid of phylogenetic importance. The presence of an additional 



, lateral tooth might, if borne out by other characters, suggest the 



' retention of a primitive character and the approach to a rhipido- 



, glossate type, yet, as we know nothing of the anatomy of this form, 



we can scarcely, from such slight evidence, regard T. triplicata, Broc, 



as being in any way more primitive than T. communis, llisso. 1 



, The radulne of the two following species of Turritella, belonging 



' to the subsection Mcsalia, Gray, differ considerably from that of 



( T. communis, Risso. They are characterized by the extreme elongation 



, of the admedian and lateral teeth. In T. lactea, Moll. [Troschel, 9] 



(pi. xii, fig. 13), the median tooth has a broad concave base; the 



recurved cutting edge consists of a large rounded median cusp, with 



two smaller cusps on either side. The admedian and lateral teeth are 



, entirely destitute of cusps or serrations, the recurved edges being 



, quite smooth. T. reticulata, Migh. [Krause, 5 J (pi. xvii, fig. 3), 



j possesses an almost identical radula, the chief difference consisting 



, in the denticulate character of the admedian and lateral teeth. 



According to Krause, this species possesses a small additional lateral 



tooth (rudimentary uncinus), comparable to the third lateral of 



T. triplicata, Broc. 



Rars [8] (pi. vii, fig. 2) has figured the radula of T. acicula, Stimp. 



In this species there are only three teeth in a transverse row, the 



laterals being absent. The shape of the teeth is very singular; they 



i are plate-like structures with strongly denticulate edges, differing 



from similar teeth in other species in that the margins are not 



, reflexed. This type of radula is utterly unlike any occurring else- 



i where amongst the Turritellidse. 



Genital organs. — The gonad of both sexes occupies the dorsal 

 portion of the visceral mass ; it is situated on the periphery of the 

 t coils, enclosing a central core of liver and bounding the posterior 

 chamber of the stomach. 



The male possesses neither penis nor accessory glands. The 

 tubular testis connects with a convoluted vas-defereus, which runs 



1 Since going to press, I have received, through the kindness of Miss Donald, several 

 specimens of T. triplicata, Broc, from Naples. A microscopic examination of 

 the radula failed to reveal the presence of an accessory lateral tooth, so that this 

 species conforms to the typical tsenioglossate condition. The general anatomy, 

 so far as I have heen able to make out from a cursory examination, appears to 

 differ in no respect from that of T. communis, Risso. The otoeyst contains 

 a single otolith. 



