This page created 9 November 2015, and last modified: 18 January 2016 (lusoria photo added)

The fifth officer listed (154.6 in Ingo Maier's numbering scheme) under the command of the Dux Britanniarum is the Praefectus numeri barcariorum Tigrisiensium, said to be stationed at Arbeia.

The numerus barcariorum Tigrisiensium has an unusual name. Barcariorum refers to a kind of boat, barcarius, that the unit presumably operated; not unlikely given the unit's station, Arbeia, is modern South Shields, near the mouth of the river Tyne. In contrast, Tigrisiensium would appear to refer to the river Tigris in far-off Mesopotamia; the upper reaches of which Rome had occupied earlier in the 4th century, but had lost to the Persians by the time the Notitia was originally compiled. Accordingly, the unit's name translates something like "the unit of boatsmen from the Tigris".

It is vaguely possible the unit might be equated with the equites Syri (102/5.255) of the Comes Britanniae: the river Tigris runs by the east of Syria and a tombstone (RIB 1065) found southwest of the fort at Arbeia records the death of a local woman whose husband came from Palmyra in Syria, and who might well have been a member of the Numerus barcariorum Tigrisiensium (the stonemason also shows signs having been a Palmyrene). However, it would be unusual, to say the least, that a unit of cavalry would have operated small vessels, so this link is probably spurious.

An inscription (RIB 601) from Lancaster referring to a N(umerus) BARC(ariorum) and its commander (praepositus) has been argued to refer to a different, otherwise unattested, unit.

That the officer of the numerus barcariorum Tigrisiensium is a prefect as opposed to a tribune would appear to rule out the unit being an infantry auxiliary unit, but does not further distinguish between cavalry, legionary, or naval status; in the Notitia, tribunes command auxiliary infantry cohorts, while it is mounted, legionary, and naval that units are commanded by prefects (however, under the Principate, auxiliary infantry cohorts were, if regular-sized, commanded by prefects, as were mounted units; tribunes commanded either legionary units or some of the milliaria-sized auxiliary infantry cohorts). Given the connection with boats, a naval classification is likely; the two other units of barcarii listed in the Notitia are also commanded by prefects: the classis barcarii (156/8.34) at Ebruduni Sapaudiae (Ebrodunum?, i.e. modern Embrun on the Durance river), which is explicitly a naval unit (classis means "fleet"), and the numerus barbaricarii (147.20; misspelled with an intrusive "bari"), stationed at Confluentibus (location unknown) and Brecantia (Brigantium; modern Bregenz on Lake Constance).

Exactly what kind of vessels barcarii were is unclear; they may be the same as the lusoriae naves ("cruisers") mentioned by Ammianus as being employed for transporting troops on rivers. Four 4th-century examples (here, here, here, and here) were excavated in Mainz in 1981-2, along with a another vessel of stouter proportions and interpreted as a patrol boat, and a sixth vessel, which was a barge.

A reconstructed Mainz-type lusoria on the river Main.
Photo by Joe Witcombe and used with kind permission.

As with all limitanei units in the Notitia, the shield pattern of the numerus barcariorum Tigrisiensium is not illustrated.

1. Ingo Maier; "Appendix 4: Numeration of the new edition of the compilation 'notitia dignitatum' (Cnd)"; last accessed 26 October 2015. See also for here for numbering examples. Return
2. D.C.A. Shotter; "Numeri Barcariorum: A Note on RIB 601"; Britannia, iv (1973) 206-209. Return
3. Ammianus Marcellinus ("Ammianus"); "Res gestae a fine Corneli Taciti", 18.2.12; available here in Latin and here in English (last accessed 8 November 2015). Return

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