THE "PORCUPINE" AND "LIGHTNING" TITNICATA. 223 



and rather wide. There is no peritnbercular area, and the dorsal tubercle is 

 small and simple, just as in Ascidia plebeia. It only occupies about one-fourth 

 of the breadth of the prebranchial zone. 



After taking all the characters into consideration, I am inclined to refer the 

 specimens to Ascidia plebeia, Alder, of which they may be considered as a 

 variety until more is known about the range of variation in the species. 



Ascidia, sp. 



A torn test of a single individual of the genus Ascidia was found adhering 

 to some fragments of Annelide tubes dredged at Station 45, lat. 35° 36', long. 

 2° 29'; "Porcupine" 1870; depth, 207 fathoms; bot. temp., 12°-4C. 



As the test only is present, it is, of course, impossible to identify the 

 species, but there can be no doubt as to the genus. I consider it worthy of 

 record simply on account of the depth from which it was obtained. 



Family Cynthiid^e. 



No members of the sub-families Cynthin.e and Boltenin^e are in the collec- 

 tion, but the Styelin^e are represented by the common Styela grossidaria, van 

 Beneden, and four species of Polycarpa, three of which appear to be unde- 

 scribed. One of these is from the Mediterranean, one from the Fseroe channel, 

 and the other from the North Atlantic S.W. of Ireland, and from outside the 

 Strait of Gibraltar, in rather deep water. 



Styela grossidaria, van Beneden. 



A large number of small individuals of this species were found attached to 

 specimens of Polycarpa pomaria, dredged near Belfast on 4th August 1869, at a 

 depth of 70 fathoms. 



They vary from 2 mm. to 3 mm. in greatest length. Although they are 

 so small, all of those I have examined are sexually mature and contain ripe 

 ova, and in some cases tailed larvae, in the peribranchial cavity. 



Also half a dozen small specimens of this species were found on a fragment 

 of shell from Station 54, lat. 59° 56' N., long. 6° 27' W., during the third cruise 

 of the "Porcupine" in 1869; depth, 363 fathoms; bot. temp.-0 o, 3 C. 



They are of the blister-like form, flattened antero-posteriorly, and with 

 expanded margins. So far as I am aware, this is the greatest depth at which 

 Styela grossularia has been obtained. It is usually regarded as a shallow water 

 species, and in some localities extends up between tide marks further than 

 any other species of Tunicate. 



There are also in the collection one large and six small specimens, labelled 

 " ' Lightning,' off Valentia." 



